ESC Biomass Handbook

Biomass in the energy industry An introduction

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Biomass in the energy industryAn introduction

Supported by BP, as part of the multi-partner Energy Sustainability Challenge, which explores the implications for the energy industry of competing demands for water, land and minerals.

Biomass in the energy industry An introduction is a study that provides contextual knowledge required for assessing the potentials and issues of using biomass for energy. The book is based on literature research and review by colleagues at the Energy Biosciences Institute (www.energybiosciencesinstitute.org) and is part of the Energy Sustainability Challenge (www.bp.com/energysustainabilitychallenge) series of handbooks. This book addresses the need for having a holistic view of the benefits and risks associated with bioenergy by studying the subject from agricultural, energy, environmental, technological, socio-economic and political perspectives. The book emphasizes that realizing the potential of biomass energy as a major player in carbon emissions reduction needs careful consideration of environmental aspects and competing demands of food, water, energy and other resources. Clear and consistent supportive policies are also required to facilitate significant financial investments for developing biomass conversion technologies and improving performance of biomass crops.

The handbook also provides key data about crops species and biomass types that are already in production or are being researched for biomass. The data includes plant characteristics, suitable growth conditions, required inputs and agricultural practices, co-products and alternative markets, as well as yield and energy productivity indicators.

The handbook offers a valuable guide for policy makers, businesses and academics on the characteristics of major biomass crops and the issues related to sustainable and responsible use of biomass for energy.

Biomass in the energy industry An introduction shows:

n What role biomass plays in the global energy context.

n What fundamental knowledge is required to understand bioenergy systems.

n How biomass is converted to energy and what technological developments are under way.

n Why it is vital to view use of biomass for energy from socio-economic, environmental and political perspectives.

n What is the potential for bioenergy and how this potential can be realized.

n Where can biomass feedstocks be grown and what are the key characteristics of biomass crops already in production or being researched for biomass.

Published by BP p.l.c. 2014 BP p.l.c.

9 780992 838713

ISBN 978-0-9928387-1-3

C4C3

Herbaceous

Plant types

Photosynthetic pathway

Propagation method

Current dominant energy use

Other

Annual

PerennialWoody Grain or seed

Seed Stemcutting

MicropropagationRhizome or root cuttings

Bioethanol Biodiesel BiogasHeat and power

Power usage

Car BarrelWeight

C3 C4

E D

C4C3

Herbaceous

Plant types


Propagation method


Other

Annual


Seed Stemcutting



Power usage

Car BarrelWeight

C3 C4

E D

C4C3

Herbaceous

Plant types


Propagation method


Other

Annual


Seed Stemcutting



Power usage

Car BarrelWeight

C3 C4

E D

C4C3

Herbaceous

Plant types


Propagation method


Other

Annual


Seed Stemcutting



Power usage

Car BarrelWeight

C3 C4

E D

Plant types

Plant characteristics icons in chapter 6

Propagation method

Annual Perennial


Plant life cycle

C4C3

Herbaceous

Plant types


Propagation method


Other

Annual


Seed Stemcutting



Power usage

Car BarrelWeight

C3 C4

E D

C4C3

Herbaceous

Plant types


Propagation method


Other

Annual


Seed Stemcutting



Power usage

Car BarrelWeight

C3 C4

E D

CAM

C4C3

Herbaceous

Plant types


Propagation method


Other

Annual


Seed Stemcutting



Power usage

Car BarrelWeight

C3 C4

E D

C4C3

Herbaceous

Plant types


Propagation method


Other

Annual


Seed Stemcutting



Power usage

Car BarrelWeight

C3 C4

E D

C4C3

Herbaceous

Plant types


Propagation method


Other

Annual


Seed Stemcutting



Power usage

Car BarrelWeight

C3 C4

E D

C4C3

Herbaceous

Plant types


Propagation method


Other

Annual


Seed Stemcutting



Power usage

Car BarrelWeight

C3 C4

E D

Primary energy use

Table 3.1Bioenergy production routes

BP Biomass HandbookTable 3.1 (20 December 2013)Draft produced by ON Communication

(Wood, straw,energy crop, etc.)

(Rape, soy, palm, etc.)

Lignocellulosic biomass

Feedstock Conversion Energy

Sugar and starch crops

Oil crops

Chemical process

Thermochemical process

Fuel for heatand/or power

Liquid fuels,transport fuels

Bioethanol

Other liquids

Biodiesel

Gaseous fuel

Biogas

Syngas

Pre-p

rocess

Biochemical process

Hydrolysis and fermentation

Transesterification

Other catalysis

Hydrogenation

Pyrolysis

Combustion

Gasification

Anaerobic digestion

Schematic diagram of bioenergy production pathways. Feedstocks on the left of the diagram are converted via a range of processes to solid, liquid or gaseous fuels on the right. No attempt is made to show relative scales of each process

Icons shown in grey indicate pre-commercial stages of adoption.

Biomass in the energy industry An introduction

First published 2014

We make no representation, express or implied, with regard to the accuracy of the information contained in this handbook and cannot accept any legal responsibility for any errors or omissions that may have been made.

Copyright 2014 BP p.l.c.

All rights reserved. No part of this handbook may be reproduced, stored in a retrieval system, transmitted or utilized in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without written permission from Cameron Rennie, BP International Ltd.

Printing: Pureprint Group Limited, UK, ISO 14001, FSC certified and CarbonNeutral.

Paper: This handbook is printed on FSC-certified Cocoon Silk. This paper has been independently certified according to the rules of the Forest Stewardship Council (FSC) and the inks used are all vegetable-oil based.

This handbook was written and edited based on literature review by Dr Sarah Davis, Ohio University; John Pierce, BP Chief Bioscientist; and John Simmons, ON Communication; analysis and research by Dr William Hay, Researcher for Global Change Solutions and Reza Haghpanah at SPENTA; and project management by Sharon Rynders, BP and Morag Ashfield, ON Communication.

Designed, illustrated and produced by ON Communication, www.oncommunication.com

For more information

BP contact: Sharon Rynderswww.bp.com/energysustainabilitychallenge

Published by BP p.l.c., London, United KingdomISBN 978-0-9928387-1-3

Reference citation

Davis, S.C., Hay, W. & Pierce, J. (2014), Biomass in the energy industry: an introduction.

The Biomass handbook is part of a series that reflects the work of the BP-sponsored Energy Sustainability Challenge.

The other titles are:

Water in the energy industry An introductionMaterials critical to the energy industry An introduction (2nd edition)

These books can be downloaded at:www.bp.com/energysustainabilitychallenge

Acknowledgements

The insights and technical information presented in this document were shaped by the research of many academic scientists associated with the Energy Sustainability Challenge (www.bp.com/energysustainabilitychallenge) and the Energy Biosciences Institute (www.energybiosciencesinstitute.org). In particular, Prof. Steven Long, Prof. Chris Somerville, Dr Heather Youngs and Dr Caroline Taylor of the Energy Biosciences Institute provided useful data, insights and perspectives throughout the drafting.

In addition, we would like to thank the following people for their guidance in the writing and structuring of the handbook and for their technical review: Dr Gran Berndes, Chalmers University; Prof. Dr Marcos Buckeridge, University of Sao Paulo; Dr Steven L Fales, Iowa State University; Dr Angela Karp, Rothamsted Research; Prof. Dr Iris Lewandowski, Universitat Hohenheim; Dr William Parton, Colorado State University; Dr Jeremy Woods, Imperial College.

We thank Matthew Trainer, Data and GIS Specialist in the Voinovich School at Ohio University, for the creation of detailed biome maps.

We are also grateful for the analytical insights and valued contributions from many colleagues within BP.

In acknowledging our gratitude to these individuals and institutions, we do not imply that they either endorse or agree with any statements or views expressed in this handbook.

Contents About this book

Contents and About this book 3

Foreword by John Pierce BP Chief Bioscientist 4

Foreword by Stephen P Long FRS Gutgsell Endowed Professor of Plant Biology at the University of Illinois, and Chief and Founding Editor, Global Change Biology 5

Units of area and Units of energy 67

1 Setting the context 8 Global energy use Biomass and bioenergy Overview of agroecosystems Water use in agriculture Agricultural production of energy crops

2 Important concepts 22 Global ecosystems and land classifications Land types Plant functional features Metrics of biomass productivity Energy issues and greenhouse gas accounting

3 Bioenergy potential 34 Current bioenergy production Global potential bioenergy production How might this global potential be realized?

Developments in biomass conversion technologies

4 Economics, the environment and politics 48 The socio-economic drivers and impacts of bioenergy Environmental sustainability The politics of biomass

5 Where can biomass feedstocks be grown? 58 Growing regions (biomes) Regional characteristics: comparison table

6 Biomass feedstock crops 70 Introduction to the selected crops Biomass crops: comparison table Biomass feedstock crops: complete list of references

Glossary 115

3

The intent of this book is to provide an introduction to the potentials and issues associated with utilizing biological materials (biomass) for energy. Detailed information is provided on various biological materials, including currently important crops and those thought to have future potential. Contextual information associated with agriculture, energy and environmental considerations is also provided.

4

Foreword by John PierceBP Chief Bioscientist

Energy is at the foundation of all economic activity. It heats us, it cools us and it lights our lives. It drives our transport, communication and computer systems, and provides the heat and mechanical work required to transform materials into a dazzling array of useful forms. Energy utilization is strongly correlated with economic well-being, and we have become adept at deriving energy from a wide range of sources. Energy is abundantly available and we use it abundantly. The majority of our energy derives from fossil fuels, and their use results in increasing concentrations of carbon dioxide in the atmosphere with worrying consequences for our climate. While we are likely to find fossil resources to fulfil our energy needs for many years to come, the pressing need to understand the effects of our energy use on our finite atmosphere, land and water resources has resulted in a burgeoning effort to find alternative renewable forms of energy with lower environmental impacts. However, any activity as large in scale as energy production requires very careful assessment and understanding of likely impacts. Approaches that are renewable in one dimension may be less so in another.

Sunlight is earths primary source of energy. Indeed, our fossil sources of energy derive from plant photosynthesis that took place long ago. The difficulty with all contemporary solar energy conversion methods is the dispersed nature of sunlight and the need to concentrate it into energy vectors that are more readily useable.Geological processes did this for us in making fossil fuels in rich, concentrated deposits, but renewable energies dependent on the sun require us to gather the energy produced over large areas. As a result, the use of such renewable energies requires significant new approaches for collection and distribution, and a sophisticated approach to land utilization.

The use of renewable biological materials as energy sources is an area of increasing focus. Plants cover the earth profusely and, using energy provided by the sun, convert carbon dioxide and water into useful organic compounds on a truly massive scale. To take advantage of this fecundity to effectively and sustainably provide a significant source of our energy needs without degrading other aspects of our environment will require diligent work to understand the scale of effort involved, the nature of the plants themselves, and how to conduct large-scale agriculture and forestry in the most environmentally responsible manner.

The impact of biomass and land availability on energy production is one of many questions being addressed in BPs Energy Sustainability Challenge programme. Researchers from a number of leading universities are collaborating in this programme to establish trusted data on the land, water, materials and ecosystems footprints of different energy pathways. BP is pleased to support this contribution concerning the role of biomass in energy production. We would like to thank all involved, and especially our colleagues at the Energy Biosciences Institute and the reviewers, who have together helped to ensure that this book is factual and well-founded.

In detailing attributes of crops and biological resources currently in use for energy production, as well as emergent energy crops and issues associated with large-scale energy production from agriculture, we hope this book will provide an accessible overview and contribute towards a more sound understanding of the use of biomass in energy.

5

The carbon dioxide (CO2) concentration of our atmosphere has been monitored at the Mauna Loa Observatory, high over the central Pacific, since 1959, when it was 316 parts per million (ppm) of air. Since then CO2 has risen at an ever-accelerating rate and on 13 May 2013 reached 400ppm a 27% increase in just over half a century, and more than 50% higher than the global pre-industrial level. Because of the differences in isotopic composition of carbon in the biosphere and that in fossil fuels, it has been shown that most of this increase is due to our use of fossil fuels. We have sufficient known fossil-fuel reserves to continue to increase CO2 concentration in the atmosphere to two and three times current levels. The physical laws of thermodynamics and radiative exchange tell us that if we increase the concentrations of long-wave radiation trapping gases, such as CO2, the earth will warm. While the details of climate change are uncertain, that climate is changing, and will continue to change substantially, is a fact. If this is not addressed, then food supply, biodiversity and our most vital ecosystem services are threatened.

At first sight bioenergy derived from plants would seem an ideal solution. Plants use energy from the sun to assimilate CO2 and trap chemical energy in the form of plant biomass. When the biomass or fuels derived from the biomass are combusted, the same CO2 is returned to the atmosphere. Thus energy is obtained for heat and work, with no net effect on the CO2 level in the atmosphere. In practice, some energy input is required to grow the crops, transport biomass and produce fuels. But with the possible exception of early corn ethanol operations, these almost always produce considerably more energy than they consume. Brazil has shown, through learning by doing, a rapid pace of improvement of its sugarcane ethanol system. By 2010 this change resulted in the sale of more ethanol for its automobiles than gasoline, and the production of a large proportion of dry-season electricity via combustion of the sugarcane bagasse.

Despite the seeming value of bioenergy, progress has been dogged by opposition, some well-intentioned and some grossly over-exaggerated, based on single issues that fail to recognize the wider feedstock options. Headlines such as Food versus fuel, Water versus biofuel, Dirtier than coal and The next kudzu have contributed to the emergence of policies inhibitory to progress, particularly toward more sustainable biofuels from perennial feedstocks. Indeed, we now have laws aimed at lowering invasive risk that apply to a crop if it is grown for bioenergy, but exempt if used for food, despite the fact that biologically, invasive risk will be the same, whatever the end use.

Bioenergy could be a major part of reduction of net carbon dioxide emissions, especially given the huge potential to improve agricultural productivity and sustainability. Realizing this key goal requires policies based on a holistic view of risks and benefits, as well as recognition of the different bioenergy feedstock options. Until now there has been no such holistic overview so, for the first time, this book provides one, outlining in one place a contemporary and forward-looking view of the issues. In addition, each current and proposed major feedstock is objectively analysed for key properties, including yield, agronomy, pests and diseases, handling logistics, environmental benefits and invasiveness. Particularly important is its illustration of the opportunities presented by a wide range of perennials that could provide substantial environmental benefits, restore ecosystem services to degraded land and use land unsuited to major food crops.

Foreword by Stephen P Long FRS Gutgsell Endowed Professor of Plant Biology at the University of Illinois, and Chief and Founding Editor, Global Change Biology

6 | 1 Introduction

6

Units of area

Figure X.XXArea comparisons

Note: all values approximated to two significant figures apart from unit conversions.

BP Biomass HandbookFigure X.XX (10 December 2013)Draft produced by ON Communication

squ

are

met

res

m2

1 10 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020

10,0

00

100,

000

1,00

0,00

0

10,0

00,0

00

1,00

0th

ou

san

d

mill

ion

bill

ion

tho

usa

nd

bill

ion

mill

ion

bill

ion

bill

ion

bill

ion

100

101 etc.

510,000,000km2 Surface of earth

150,000,000km2 Global land area

5,500,000km2 Amazon rainforest

Global maize harvest1,800,000km2

Texas700,000km2

Cuba110,000km2

Hong Kong1,000km2

Paris100km2

Central Park, New York3.4km2

Vatican City44km2

1 square kilometre (1km2)100Ha

1 hectare (ha)10,000m2

Tiananmen Square, Beijing44Ha

Professional football playing area7,000m2

1 acre4,047m2

Basketball court420m2

Standard parking space10m2

Average bath towel1m2

Table tennis table4.2m2

Lebanon10,000km2

Hyde Park, London1.4km2

1 Introduction | 7

7

Units of energy

Figure X.XXArea comparisons

Note: all values approximated to two significant figures apart from unit conversions.


squ

are

met

res

m2

1 10 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020

10,0

00

100,

000

1,00

0,00

0

10,0

00,0

00

1,00

0th

ou

san

d

mill

ion

bill

ion

tho

usa

nd

bill

ion

mill

ion

bill

ion

bill

ion

bill

ion

100

101 etc.

510,000,000km2 Surface of earth

150,000,000km2 Global land area

5,500,000km2 Amazon rainforest

Global maize harvest1,800,000km2

Texas700,000km2

Cuba110,000km2

Hong Kong1,000km2

Paris100km2

Central Park, New York3.4km2

Vatican City44km2

1 square kilometre (1km2)100Ha

1 hectare (ha)10,000m2

Tiananmen Square, Beijing44Ha

Professional football playing area7,000m2

1 acre4,047m2

Basketball court420m2

Standard parking space10m2

Average bath towel1m2

Table tennis table4.2m2

Lebanon10,000km2

Hyde Park, London1.4km2

Figure X.XXEnergy comparisons


jou

les

1 10 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020

10,0

00

100,

000

1,00

0,00

0

10,0

00,0

00

1,00

0th

ou

san

d

mill

ion

bill

ion

tho

usa

nd

bill

ion

mill

ion

bill

ion

bill

ion

bill

ion

100

101 etc.

kilo k

meg

aM tera T

pet

aP ex

a E

gig

aG

5 x 1020JWorld energy consumption in 2010

1.9 x 1020JGlobal annual oil production

Solar energy received on earth every minute 6 x 1018J

Average power plant annual output 3.2 x 1016J

Oil passing through the Strait of Hormuz each hour 4.6 x 1015J

Typical road tanker full of gasoline1 x 1012J

One tonne of bioethanol3 x 1010J

Energy in one barrel of oil5.7 x 109J

Energy content of 1kg of maize1.6 x 107J

One megawatt hour (MWh)3.6 x 109J

One kilowatt hour (kWh)3.6 x 106J

Running a large television for one hour1 x 106J

Dietary energy in 100g dark chocolate2.2 x 106J

Dietary energy in one large apple4.2 x 105J

One kilocalorie or dietary Calorie4.18 x 103J

One British thermal unit (btu) = 1,055J1.055 x 103J

One calorie4.18J

Heating one gram (nearly one litre) of air through one degree Celsius1J

Energy content of one hectare of miscanthus5 x 1011J

Recommended human daily calorific intake1 x 107J

World population is forecast to reach 8.3 billion by 2030, and societies are becoming more affluent. Global energy use is rising with population growth and increased consumer demand, and there are concerns about the resulting carbon dioxide emissions to the atmosphere. Renewable energy offers a mechanism to reduce carbon emissions, and its production is expected to grow faster than overall energy growth through to 2035.

Biomass the solid matter in biological organisms can be converted into biofuels, heat and power, and biogas. Global use of bioenergy is expected to more than double by 2035, with heat and power being the largest consumers. Liquid transport fuels currently account for less than 5% of current bioenergy, though production is rising fast. Most biofuels are currently derived from crops that are also food for humans and animals, but non-food plants are also being investigated for their potential as biomass crops.

Societies throughout the world have converted significant areas of forests, savannah and shrubland into crop and pasture lands, while advances in technology and plant breeding have led to prodigious yield increases in commercial food and fibre crops. Similar improvements are expected for dedicated energy crops; these could potentially be grown on land currently less suitable for food production.

While economic and practical realities will limit the rate and extent of change possible, there is substantial land and technology available for improving the overall output of both food and biomass.

8

1 Setting the context | 9

1 Setting the context

Global energy use

The worlds energy use is complex and changing. Total energy use rises with population and economic activity, and technological and commercial innovations affect the type of energy used. As a result, the amount and type of energy use varies throughout the world depending on both technology and available resources.

Figure 1.1 shows how sources of energy differ across regions and by level of economic development. Biomass currently provides a very small portion of energy use in developed countries, whereas biomass is a primary energy source for heating and cooking in many developing countries. The reliance on biomass in Africa relative to all other regions is clearly shown, as is the relatively small contribution from renewable sources worldwide.

Population and income growth are the key drivers of the growing demand for energy. These factors and the development of energy-hungry technologies from the time of the Industrial Revolution to the present day are reflected in the energy demand curves shown in Figure 1.2. By 2030 the world population is projected to reach 8.3 billion, which means an extra 1.3 billion people will need energy; and world income in 2030 is expected to be roughly double the 2011 level in real terms[1].

Biomass

MiddleEast

LatinAmerica

Africa

Non-OECDAsia

EasternEurope/Eurasia

OECD AsiaOceania

OECDEurope

OECDAmericas

World

Per cent energy use by source tCO2/person

Hydro Other renewables

Nuclear Gas Oil Coal

4.7

17.1

7.2

9.0

5.1

4.6

5.9

0.9

2.8

Figure 1.1

BP Biomass HandbookFigure 1.1 (10 February 2014)Draft produced by ON Communication

Figure 1.1 World energy use in percentage terms by region and by source in 2010. Each square in the regional stripe represents 1%. The major fossil and renewable fuels are shown in different colours. Circles show tonnes of CO2 emissions per capita in 2009[2, 3].

This chapter provides an introduction to the use of biomass for energy in the context of global energy use, the evolution of agriculture and projections for future uses of biomass.

10 | 1 Setting the context

Figure 1.2 Global use in exajoules (EJ) of the six most important energy sources since 1850. Historically, biomass use is mainly the traditional use of fuelwood; the renewable curve includes all modern renewable sources except biomass. Major technology advances are shown and also significant changes in energy source: coal replacing biomass in the Industrial Revolution; the increase in oil with the rise of the internal combustion engine; and gas for heating and power generation[4].

Figure 1.3 The increase in energy demand in billion tonnes of oil equivalent (toe), excluding biomass used for heat and cooking from 1990 to the present day, and projections until 2035. The effect of the global economic crisis from 2008 can be seen clearly[5].

Prim

ary

ener

gy

(EJ)

500

400

300

200

100

0

1850 1900 1950 2000

Vacuumtube

Television

Microchip

Nuclearenergy

Commercialaviation

Gasolineengine

ElectricmotorSteam

engine

Biomass Coal Oil Gas Nuclear Other renewables

Figure 1.2

BP Biomass HandbookFigure 1.2 (20 Decmber 2013)Draft produced by ON Communication

Despite increasing energy efficiency, energy consumption is on the rise globally as shown in Figure 1.3. World primary energy consumption is projected to grow by 1.5% per year from 2012 to 2035, adding 41% to global consumption by 2035. The fastest-growing fuels are renewables (including biofuels), with growth averaging 6.4% per year from 2012 to 2035. Nuclear (2.6% per year) and hydro (2.0% per year) are both projected to grow faster than total energy consumption.

Among fossil fuels, natural gas use has grown the fastest (1.9% per year), followed by coal (1.1% per year) and oil (0.8% per year)[5]. The lower relative growth rates of fossil fuels, however, apply to a very large base of use. On an absolute energy basis, for example, coal use grew the most in the period 2000 10 and the additional use of coal constituted almost 50% of the total increase in energy use.

Oil CoalGas

Figure 1.3

Nuclear Other renewables(includes biofuels)

Hydro

BP Biomass HandbookFigure 1.3 (11 June 2014)Draft produced by ON Communication

1990 2005 2020 2035

Billi

on to

e

EJ

100

200

300

400

500

600

700

00

18

15

12

9

6

3

Note: 1toe equals approximately 42 gigajoules.


Biomass and bioenergy

Biomass refers to the matter in all biological organisms, but in the context of energy it is most commonly used to mean the solid material that can be harvested or collected from biological organisms primarily from plants. This meaning is used throughout this handbook (definitions for terms used in this book that are unfamiliar or that have various meanings in common usage may be found in the Glossary at the end of this handbook). Major components of biomass include sugars, starches and oils produced from plants. These are extracted in great abundance today for energy production. The term biomass also includes the heterogeneous material found in even greater abundance in materials such as wood, plant stems and husks. All these materials can be converted into an energy form useful for heat, power and transport fuel.

Bioenergy is a general term referring to energy derived from any renewable biological material from plant matter, animals or organic wastes derived from plant and animal matter. In this handbook we focus primarily on the conversion of materials from plants (biomass) into bioenergy.

Bioenergy is produced from biomass in a number of ways, including:

Biofuels: liquid fuels mainly used for transport, produced by a variety of thermochemical and biochemical processes. These fuels can come from a wide range of plant and animal materials. The predominant forms today are bioethanol (derived from fermentation of sugars) and biodiesel (from esterification of plant and animal oils) with increasing amounts of the oils being treated with hydrogen to create hydro-treated vegetable oils (HVO) suitable for diesel use. A variety of new fuel

molecules are also at the research and early commercial demonstration phases. For instance, liquid biofuels derived from lignocellulosic biomass that has undergone thermochemical or biochemical processes are just beginning to appear in commercial quantities.

Heat and power: this includes the traditional form of bioenergy in which plant materials (such as wood or grasses) are collected and burned for heat. This heat can be used to generate electrical power as well. Early, large-scale adoption has often involved a mixture with coal for the generation of power as shown in Figure 1.4.

Biogas: a combustible gas produced by the anaerobic digestion of biological material. Biogas consists of a number of different compounds and hydrocarbons, the main ones being methane and carbon dioxide. It is produced from a wide range of materials, particularly wastes (especially those with relatively high water content), and from landfill. It is used primarily for electricity and heat generation. Biogas from anaerobic digestion should not be confused with syngas, which can be derived from both fossil and renewable sources of carbon (biomass). Syngas has a very different chemical composition (being composed of carbon monoxide and hydrogen) and is both made and used in a very different manner. Biogas itself can be converted to syngas for use in the production of fuels, but this is not a significant current practice.

Production routes of biomass to various fuels are discussed in greater detail in Chapter 3 with a summary provided in Table 3.5 and a schematic outline on the inside front cover of this book.

Figure 1.4 Woody biomass being blended with coal at a Colorado electricity generating plant to provide a mixed feedstock boiler fuel[6].


Biomass can also be used on a large scale in the production of industrial chemicals. Current processes primarily focus on converting starch and sugar into the desired chemical products, using microorganisms modified to produce the chemical of interest. In many ways these processes resemble those used to produce biofuels such as ethanol. This is an area of much research and commercial interest, and new processes and facilities continue to appear. Given the volumes of materials needed for the chemical sector, the overall use and demand for biomass for chemicals is much lower than that for energy.

Globally and traditionally, the largest use of bioenergy is for so-called direct use. This traditional use of bioenergy is mainly for heating and cooking, using biomass sources such as wood, charcoal, crop residues and animal dung. Much of it is used in small domestic stoves and open fires, and statistical data are therefore limited. Even in OECD countries, two-thirds of total bioenergy use is for heating, much of it sourced through forestry management. Figure 1.5 is a chart originally published by the International Energy Agency (IEA) depicting the use of bioenergy by sector in 2010 along with the potential use in 2035. The future estimates are based on the IEAs New Policies Scenario, which takes into account broad policy commitments and plans to address energy-related challenges, even if the specific measures to implement these commitments are yet to be defined.

In this assessment, the total amount of traditional biomass consumed is expected to decline slightly over time, as access to modern fuels increases around the world. Excluding the traditional use of biomass, global primary use of bioenergy is expected to more than double from 22 exajoules (EJ) in 2010 to nearly 50EJ by 2035, growing at an average rate of 3.3% per year. Provision of heat and power are projected to be the largest consumers of non-traditional bioenergy, potentially growing from nearly 17EJ in 2010 to more than 37EJ by 2035. Together, these two sectors account for about two-thirds of the additional consumption of bioenergy in the IEA scenario.

A little more than 10% of current non-traditional bioenergy is in the form of liquid fuels for transport (i.e. biofuels). Brazil and the US are the largest producers of bioethanol, and Germany is the largest producer of biodiesel. The use of biomass for electricity generation (such as bagasse in Brazil and woodchip- and pellet-fuelled power generators in the UK) accounts for just over 20% of current non-traditional bioenergy.

Bioelectricity continues to grow in both OECD and non-OECD nations. In 2011 more than 35 countries had bioelectricity capacities exceeding 100 megawatts (MW). Total generation has increased by more than 170 terawatt-hours (TWh) (0.6EJ) from 2000, reflecting an 8% annual growth rate over the past decade[7]. With more than 100 countries enacting renewable electricity targets, bioelectricity is expected to grow. The IEA estimates that electricity generated from biomass could grow to 530TWh (1.9EJ) in 2017 and possibly to more than 1,470TWh (5.3EJ) in 2035, depending on the cost and availability of biomass.

While much work has been done to map the potential for global biogas production, there is little reliable data about current biogas production levels in many countries. While the contribution (in energy terms) is relatively small, biogas was used to produce roughly 3% of electricity use in Germany[8], provided heating and cooking fuel to nearly 40 million Chinese households[9], and made up 64% of the gas use for transportation in Sweden in 2010[10]. There is increasing production and local use of biogas from landfills, and growing interest in utilizing anaerobic digestion of biomass for biogas and production of electricity.

Heat and power production are, and are expected to continue to be, the largest uses of biomass, enabled by well-known and widely practised combustion technology. However, biofuels for transport are also expected to more than double by 2035, and significant research is under way to provide more cost-effective conversion technologies to enable more penetration into the transport sector with fewer environmental impacts than are currently associated with liquid fuels.

Figure 1.5 Use of bioenergy by sector in 2010 and 2035 (projected by the IEA for conditions where new policies are implemented). Use is estimated to rise from 53EJ in 2010 to 79EJ in 2035. The proportion used for heat by traditional methods (heating and cooking) is projected to fall considerably; the proportion used for heat via modern methods of production remains almost unchanged; while proportions used for power and transport by modern methods make significant increases[2].

Figure 2.6aUse of bioenergy by sector in 2010 and 20351

Total 53EJ

BP Biomass HandbookFigure 3 (10 February 2014)Draft produced by ON Communication

Traditional58.8%

2010 2035

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BP Biomass HandbookFigure 1.6 (20 December 2013)Draft produced by ON Communication

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Although biofuels currently supply only a small fraction of liquid transport fuels, production has been rapidly rising. Crops used to produce both food and fuel dominate today, though crops grown specifically for energy use are expected to increase in the future. While future projections of biofuels production are notoriously difficult to quantify, and the types of crops used and fuels made are subject to numerous technical, economic and political considerations, recent analyses suggest that biofuels could constitute approximately 6% of liquid transport fuels by 2035[2], with around three-quarters of the production continuing to come from North and South America[1]. Figures 1.6 and 1.7 provide example perspectives on the current and future mix of feedstocks for the supply of

biofuels to 2020. This projection, from the UN FAO, shows negligible growth of ethanol based on grains such as corn, the most significant source today, with growing volumes from sugarcane and, later in the projection, cellulosic biomass crops. Biodiesel is produced, and is expected to be produced, at much lower volumes (note different scales used in the graphs). Vegetable oil is projected to remain the most widely used source of biodiesel by volume. Waste oils, fats and tallows, as well as new crops with high oil yields and an ability to grow in diverse habitats (as exemplified by Jatropha in Figure 1.7), are anticipated to become a richer part of the mix.

Figure 1.6 Current and future mix of volumes of bioethanol supplied for fuel use projected annually to 2020[11].

Figure 1.7 Current and future mix of volumes of biodiesel supply projected annually to 2020[11].


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The bioenergy production chain consists of four main stages as shown in Figure 1.8. Biomass is grown, collected and often treated or densified into transportable forms such as bales, chips, billets or pellets to allow economical movement to the conversion facility. Following conversion to an alternate energy carrier such as electricity, heat, steam, liquid fuel or gas, the bioenergy can be distributed for end use in homes, vehicles and industry.

Biomass cultivation can encompass a wide variety of practices used in conventional agriculture and forestry. Where residues or wastes are the biomass source for energy, the production chain may begin with collection

and treatment, since primary cultivation is for other purposes including food, feed or timber production.

There are many ways to convert raw biomaterials into fuels. Active development worldwide is improving the various process efficiencies and widening their utility for different feedstocks (see Chapter 3 for more details on conversion processes).

As the use of bioenergy grows, there is increasing interest in developing new types of crops that produce a large amount of biomass per hectare and are grown specifically to supply energy. These plants are known as energy crops, examples of which are detailed in Chapter 6.

Figure 1.8 The four main stages of bioenergy production.

Biomasscultivation

Collection,densification,

transport and storage

Conversion toenergy carrier

Distributionand end use

Figure 1.8

BP Biomass HandbookFigure 1.8 (18 November 2013)Draft produced by ON Communication

What makes an energy crop?

The first criterion for any energy crop is that it should be productive in terms of biomass yield per hectare to minimize the land area required. Second, the physical and chemical characteristics of the crop must be suitable for the conversion technology that will convert it into biofuel, biogas or power. For energy crops to make significant impacts on energy use, they must be grown on a large scale, so questions of sustainability (economic, environmental and social) must also be considered. The following characteristics are key traits that facilitate environmental sustainability:

Characteristics of an ideal bioenergy crop [1214]

High-energy yield per unit growing area. Low-input, low-cost processing requirements. Low greenhouse gas (GHG) emissions and energy

requirements. Easy to establish. Tolerant to extreme and/or variable environments. High efficiency of nutrient use. High efficiency of water use. Provide additional ecosystem services

and/or co-products. Suitable for a range of conversion processes into

various forms of bioenergy. Productive on soils and topographies less suited to

food crops. Low- or zero-invasive potential. Unrelated to native or major weed species to avoid

spread of genes and potential disruption of native ecosystems.

Inevitably, no single crop will meet all of these requirements, and the importance of a particular requirement depends on location. Chapter 6 of this handbook lays out the extent to which alternative energy crops address these requirements in different locations.

As a general rule, perennial crops meet many of these requirements: they do not require annual tillage and planting, and they often recycle nutrients and add carbon to the soil. As explained in Chapter 3, most

advanced biomass crops (both current and potential) are perennials, either trees or perennial grasses. Complex choices between maximizing yield and maximizing sustainability, however, have to be made. For example perennial grasses such as switchgrass and miscanthus can be highly productive in temperate environments. In the autumn these grasses transfer their nutrients to the root system so they can be retained over winter, even if the plant is harvested. Production in temperate environments is limited to the warm period of the year, and is therefore less productive than in moist subtropical and tropical environments where production is possible throughout the year. On the other hand, in environments with no dormant season, material must be harvested green. This gives higher yields but there are costs associated with drying fresh grass, and in this scenario there is less recycling of nutrients to the root system.

Geographical, topographical and social factors can also affect the choice of bioenergy cropping systems. As a crop, oil palm, for example, is not inherently less sustainable than other plantation crops. But many areas suitable for oil palm are naturally forested, so the conversion of carbon-rich peat-swamp forests in parts of South-East Asia can have environmental impacts that outweigh any benefit from producing renewable biofuel. Conversely, the introduction of perennial grass feedstocks on intensively managed land can create net carbon and GHG benefits through restoration of soil carbon and interception and reuse of nutrients. Indeed, the use of perennials as bioenergy sources can broaden opportunities for sustainable agricultural production: some grasses can stabilize eroding slopes, others tolerate saline soils, while succulent plants thrive in semi-arid areas.

Trade-offs between different crops are inherent in all forms of agriculture. As large new areas of bioenergy crops are contemplated, it is essential to minimize environmental impacts. Land resources are not infinite, so production of bioenergy crops must be carefully balanced with other uses for land, such as food, animal feed and material production.


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Overview of agroecosystems

After the emergence of agriculture about 10,00012,000 years ago, agricultural productivity increased slowly until the advent of mechanization in the 18th century, when horse-drawn drills, reapers and threshing machines allowed more land to be cultivated and also brought greater yields. The invention of the steam engine and steam plough increased productivity further and allowed previously unproductive land to be tilled. These gains were enhanced when tractors driven by internal combustion engines came to the market in the early 1900s. A modern tractor and plough can till many times more land in a day than a person with a horse, and combine harvesters reap in an hour what teams of people could only achieve in days.

Other agricultural practices have also improved dramatically. Crop rotation began in the 18th century. In the 19th century, more sophisticated fertilizer treatments emerged, along with increasing numbers of research organizations that advised farmers on best practice and introduced new strains of plants. The 20th century saw genetics and chemistry playing an increasing part in agriculture. The introduction of hybrid maize and dwarf wheat allowed dramatically improved yields; the HaberBosch process for fixing nitrogen allowed ammonia-based fertilizers to become cheaply available; and organic chemists developed a wide range of effective pesticides and herbicides. In the late 20th century and through to today, genetic marker-assisted plant breeding and genetic engineering (also known as genetic modification or genetic manipulation) have become hallmarks of the next revolution in agriculture in many parts of the world, spearheaded by large research organizations.

The application of all these technologies has driven prodigious improvements in the yields of many crops. Since 1961, for example, average yields of sugarcane and corn have increased by 41% and 166% respectively, as shown in Figure 1.9. The most favoured growing locations have seen even more dramatic yield improvements. These improvements have occurred steadily over decades while, at the same time, different crops have been developed to

respond to the changing demands for food, feed, fuel and materials. Future energy crops, such as those discussed in this handbook, would be expected to benefit from the same types of investment.

In addition to the changing nature of agriculture, the amount of land devoted to it has expanded significantly. Across the globe, cropland and pasture has expanded at the expense of primary forest, savannah and shrublands, as shown in Figure 1.10. Growth has been driven primarily by a rise in population and by the changing dietary intake of more affluent consumers.

Figure 1.10 Change in land use during various periods since 1765[16]. The figures on top of each category show the land-use change between 1765 and 2005, in million km3.

Figure 1.9 Increasing yields of sugarcane and maize grain over 50 years compared with yields in 1961. Moisture contents of 70% for sugarcane and 15% for maize grain were assumed[15].

23.7 +8.3 +0.4 5.4 6.8 1.7 +0.5 +9.4 +19.3


Increasing demand for meat proteins, as shown in Figure 1.11, driven by population growth, economic growth and changing dietary habits, is directing more and more resources into meat production. From an energy perspective, livestock production is quite inefficient. Intensive beef production, for example, commonly utilizes grains for feed, and can require 620kg grain/kg beef produced[17]. While there is continuous development in methods to improve the efficiency of meat production, it is estimated that 70% of all agricultural land is used in pastoral, mixed-system and intensive livestock production. Food, feed and energy uses will all compete for available land.

Despite the overall increase in land area devoted to agriculture, there are areas where farming has been abandoned across large regions. Some of this abandoned agricultural land has become reforested and is now valued for recreation, biodiversity and important carbon stocks (growing forests remove substantial amounts of carbon dioxide from the atmosphere). Many re-established forests, such as large areas of the eastern US, are actively managed for wood resources. Residual wastes from timber extraction and saw milling have increasingly been used for energy in the wood-products industry and can potentially provide bioenergy feedstock to other sectors (see Forest biomass box below).

Abandoned agricultural land that has not returned to forest or native ecosystems has, in many places, been developed for urban and residential use. Recently abandoned land, however, may also be shifting in and

Figure 1.11 The growth in demand for meat proteins for developed and developing countries[17, 18].

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out of agricultural production due to changing land ownership or altered economic incentives. Developing recently abandoned land for bioenergy production would have less environmental impact than developing land on which indigenous ecosystems have regenerated. It would also help maintain food production capacity that might be required in the future.

Forest biomass

Woody biomass is used for 80% of traditional primary energy use, totalling nearly 32EJ per year and supplying nearly 2 billion people with heat and cooking fuel. In developed nations, wood typically supplies less than 5% of primary energy. In the US, for example, wood is used to supply 1% of the electricity supply and 2% of primary energy, mainly to industrial users. Finland and Sweden are exceptions with nearly 19% of primary energy generated as heat and power from woody biomass[19,20].

The total potential for woody biomass could be as high as 110EJ per year (EJ/yr), according to the Intergovernmental Panel on Climate Change; however, the sustainable and acceptable limits of forest biomass use are still under debate and the use of forest biomass for energy is controversial. Historic depletion of forest resources in many parts of the world has instilled caution in communities considering re-expanding use of wood biomass for energy. In parts of the US, Canada, the EU and China, forest biomass is actually accumulating. Growing stock in the EU has increased nearly half a per cent per year for the past 23 years and US forest biomass has increased by 10% in a 10-year period. In the US and Canada, less than 1% of available forest biomass is currently harvested for all uses. The increase in tree stand density, increased dead woody biomass, and increasing climate stress have been implicated in more frequent and more severe forest

fires. Whether increased forest management will result in a sustainable and acceptable supply of biomass for bioenergy is not yet clear.

The situation for tropical forests is still worrisome. Forests in South America and Africa are still experiencing net losses, although deforestation has slowed in many regions including the Brazilian Amazon. Although an increase in tropical forest plantations for fruit, oil seed and timber production may eventually be a source of residual biomass for energy in some regions, such biomass may not be considered acceptable by some stakeholders. See Chapter 4 in this handbook for a discussion of sustainability criteria in policy.

Forest ecosystems can be very productive and offer some advantages to herbaceous energy crops. Trees store carbon, both above ground and in the soil, over a very long time period and so can be left as standing stocks. Herbaceous crops must be harvested before or soon after senescence or they will degrade and release their carbon. Trees can be grown on steeply sloping land and tolerate a wide range of soils and hydrologies. Finally, forests can provide a more diverse set of ecosystem services, but because forests are more complex and require longer rotations to accumulate biomass, a careful and detailed understanding of each forest system is required to assess long-term sustainability.


Figure 1.12Global Sankey diagram for annual fresh water withdrawn for human use [25]. From left to right, the diagram illustrates the continental distribution of withdrawals, the sectors (agriculture, industry, domestic) in which the water is used, the services provided by the water, and finally the return of the water to the hydrological cycle. Share of agriculture in total withdrawals is shown in yellow. In the final (right-hand) segments, changes in water quality during its use are indicated in different colours. The red segment indicates where energy is used in treating wastewater. The vertical width of each bar in the diagram is proportional to the volume of fresh water involved, measured in cubic kilometres (km3), and numerical amounts are provided with labels, also in km3.

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Water use in agriculture

All biomass requires water to grow. The intensity of water use is determined by the volume of water withdrawn from local freshwater sources and subsequently consumed in their growth. Worldwide, about 80% of cropland is rainfed (not irrigated[21]) and provides about 60% of global crop production [22]. The remaining 20% of cropland, about 250 Mha[23, 24], is irrigated during at least part of the growing season and yields about 40% of all production. Freshwater withdrawals for agricultural irrigation constitute some 2,700km3 of water (or about 70% of world withdrawals) as shown in Figure 1.12, a Sankey diagram that illustrates the fate of water withdrawn for human use[25]. While many factors impact crop yield, the dominant factor in determining where irrigation is needed is the amount of rainfall. This varies dramatically: from desert regions where precipitation is rare to regions with more than a thousand millimetres of precipitation per year. As with food crops, the amount of water used for irrigation of biomass crops will be highly dependent on local conditions and the type of plant used.Common practice to date for the production of liquid biofuels has been to grow crops where little or no irrigation is needed. As a result, the intensity of water use for growing these crops is much lower than for agriculture on average, with estimates of about 0.5% of world freshwater withdrawals for 2010 biofuels production[26].

The water cycle (in which plants participate) involves the set of processes by which water circulates between the earths oceans, atmosphere and land. It involves precipitation as rain and snow, drainage in streams and rivers, and return to the atmosphere by evaporation

and transpiration. This water cycle provides essential ecosystem services. Regardless of whether vegetation is native or non-native, evaporation and transpiration affect the water flows into local streams and rivers. Vegetation thus plays a part in flood control.

Plants obtain the water they need from the soil via their roots. Soil water comes from precipitation, groundwater and from irrigation. Water is lost from the soil by evaporation, drainage and uptake by plants, with different types of plant cover withdrawing water at different rates. Plants take up far more water than they ultimately use in photosynthesis or store within their structure.

The remainder is released into the atmosphere (in a process called transpiration) to be recycled as rain. Plant canopies intercept some rainfall before it reaches the soil; this water is then lost through direct evaporation from the leaves. This loss can be particularly important in densely planted agricultural crops with complete canopy closure. Because the periods of highest rainfall in the year may be out of phase with crop demand for water, storage of water in the soil plays an important role in supporting crops. The capacity of the soil to store water that is accessible to plants depends on the soil texture. Sands absorb water rapidly, but can store little and drain quickly. Clay soils will not absorb water rapidly, making run-off and erosion more likely. Once they do absorb water, clay particles bind water molecules, so some of the water is not available to the crop. Soil organic matter is critical in increasing the water-holding capacity of soils.


Evaporation and transpiration provide another essential ecosystem service by cooling continental surfaces that could otherwise be much warmer at the height of summer. At the same time these processes provide water to the air, which in turn falls as rain elsewhere. Indeed a major concern of Amazon deforestation is that it could cause

increased regional droughts because less water will be evaporated. Other types of ecosystem services provided by plants include reduced loss of nitrate and other elements due to changes in peak flow drainage, and reduced soil erosion.

Agricultural production of energy crops

A primary driver for promoting energy crops is the desire to lower the amount of GHG associated with energy production and to find cheaper and more sustainable ways to produce biomass. It can be hard, however, to quantify the issues: economic data are difficult to pin down, with yields and prices for crops varying dramatically over time and regionally. There is also an imbalance in the amount of data available: we have plenty of information about traditional crops used in our food systems, whereas large-scale production of energy crops is still in its infancy. As a result, much of the information on energy crops is based on extrapolation from small datasets and emerging research findings. Chapter 3 of this handbook provides more details on the energy potential from biomass and issues associated with its large-scale production.

Although food production is the main purpose of agriculture, our farming systems also produce a wide range of non-food goods and services. As the worlds population grows and demands more resources from a finite amount of land, there is a need to prioritize these items. Goods and services arising from agriculture include food crops and

livestock, energy, organic materials (such as wood and cotton), specialist materials (such as bioplastics and other large-volume chemicals), carbon sinks, biodiversity and other ecosystem services. Ultimately, land will be used in a way that gives the highest economic return, and this will differ by location and by prevailing policy and regulation.

Our need for food remains paramount. To feed our growing population, we will need higher yields of existing crops, as well as new crops that can be grown on land currently less suitable for agriculture. Figure 1.13 provides a view of the distribution of land areas around the world with differing suitabilities for agriculture. Productivity of crops grown in different regions can vary manyfold with crop genetics and agricultural practice significantly impacting output. Major land areas, for example in Africa and the Ukraine, are currently producing substantially suboptimal yields.

One way to achieve significant increases in biomass production without compromising food resources is by converting marginal and abandoned land to bioenergy production. This could be done by replacing poorly

Agricultural suitability across the globe

n Closed forestn Inland water bodiesn Irrigated arean Land prime or well suited for agriculture

n Land suited for agriculturen Land unsuited to poorly suited for agriculturen Protected arean Urban area

Figure 1.13 Suitability of land with appropriate levels of inputs for pasture and rainfed crops[27].


performing crops with better alternatives as they become available and developing crops that can be grown on saline, water-logged or arid lands that cannot (economically speaking) support food production. Investments in bioenergy systems might even rehabilitate such land so that it could be used for future food production.

Many agricultural systems already yield more than one type of product simultaneously. For instance, when cereal crops are used to produce bioethanol, between a quarter and a third of the total weight of the grain is available after processing as a high-protein feed (known as distillers grains). Cotton produces cotton oil and cottonseed meal as well as fibre (cellulosic cotton lint). Excess straw can

be used for heat and power production or as feedstock for lignocellulosic biofuels. Similarly, the use of wood harvested from rubber and palm-oil plantations at the end of a plantations economic life does not displace the production of rubber or palm oil, but facilitates the replanting of such crops.

All of these approaches and more (increasing productivity and yield, diversifying crop patterns, bringing marginal land into cultivation and developing multi-use crops) will be needed to achieve significant expansion of agricultural output while minimizing environmental damage.

Chapter references[1] BP (2013), BP energy outlook 2030. BP, London, UK.

Available from: http://www.bp.com/content/dam/bp/pdf/statistical-review/BP_World_Energy_Outlook_booklet_2013.pdf [accessed July 2013].

[2] IEA (2012), World Energy Outlook 2012. International Energy Agency (IEA), Paris.

[3] The World Bank, Data Indicators Databank CO2 Emissions. Available from: http://data.worldbank.org/indicator/EN.ATM.CO2E.PCcountries/1W?display =graph [accessed February 2014].

[4] Adapted from Nakicenovic, N. (2009), Supportive policies for developing countries: a paradigm shift. Background paper prepared for World Economic and Social Survey 2009.

[5] BP (2014), BP energy outlook 2035. BP, London, UK. Available from: http://www.bp.com/content/dam/bp/pdf/Energy-economics/Energy-Outlook/Energy_Outlook_2035_booklet.pdf [accessed February 2014].

[6] Kryzanowski, T. (2009), Big energy win with biomass, enrG Magazine. Available from: http://www.altenerg.com/back_issues/index.php-content_id=231.htm [accessed July 2013].

[7] International Energy Agency (2013), Tracking clean energy progress 2013: IEA input to the clean energy ministerial. OECD/IEA, Paris. Available from: http://www.iea.org/publications/TCEP_web.pdf [accessed February 2014].

[8] German Biogas Association (2013), Entwicklung des jhrlichen Zubaus von neuen Biogasanlagen in Deutschland (Stand 11/2013). Available from: http://www.biogas.org/edcom/webfvb.nsf/id/DE_Branchenzahlen/$file/14-07-01_Biogas%20Branchenzahlen_2013-Prognose_2014.pdf [accessed February 2014].

[9] Global Methane Initiative, Country profile: China. Available from: https://www.globalmethane.org/documents/ag_cap_china.pdf [accessed February 2014].

[10] Swedish Energy Agency (2011), Biogas in Sweden factsheet. Available from: http://www.energimyndigheten.se/Global/Internationellt/Exportfr%C3%A4mjande%20o%20Bilateralt/Biogas_Sweden_Faktablad_HR.pdf [accessed February 2014].

[11] OECDFAO (2011), OECDFAO agricultural outlook 20112020. Available from: http://www.oecd.org/site/oecd-faoagriculturaloutlook/48178823.pdf [accessed February 2014].

[12] Dale,V. H., Kline, K. L., Wright, L. L., Perlack, R. D., Downing, M. & Graham, R. L. (2011), Interactions among bioenergy feedstock choices, landscape dynamics, and land use, Ecological Applications, vol. 21, pp. 10391054.

[13] Davis, S. C., Boddey, R. M., Alves, B. J., Cowie, A. L., George, B. H., Ogle, S. M., Smith, P., van Noordwijk, M. & van Wijk, M. T. (2013), Management swing potential for bioenergy crops, GCB Bioenergy, vol. 5, pp. 623638.

[14] US Department of Energy (2006), Breaking the biological barriers to cellulosic ethanol: a joint research agenda. Report from the December 2005 workshop, DOE/SC-0095. Department of Energy Office of Science. Available from: http://genomicscience.energy.gov/biofuels/2005workshop/2005low_feedstocks.pdf [accessed February 2014].

[15] Food and Agricultural Organization of the United Nations. FAOSTAT database. Available from: http://faostat3.fao.org/home/index.html#HOME [accessed February 2014].

[16] Adapted from Meiyappan, P. & Jain, A.K. (2012), Three distinct global estimates of historical land-cover change and land-use conversions for over 200 years, Frontiers of Earth Science, vol. 6, no. 2, pp. 122139.

[17] Giovannucci, D., Scherr, S., Nierenberg, D., Hebebrand, C., Shapiro, J., Milder, J. & Wheeler, K. (2012), Food and agriculture: the future of sustainability. United Nations Department of Economic and Social Affairs, Division for Sustainable Development, New York. Available from: http://www.un.org/esa/dsd/dsd_sd21st/21_pdf/agriculture_and_food_the_future_of_sustainability_web.pdf [accessed October 2013].

[18] Kanaly, R., Manzanero, L., Foley, G., Panneerselvam, S. & Macer, D. (2010), Energy flow, environment and ethical implications for meat production. UNESCO, Bangkok. Available from: http://unesdoc.unesco.org/images/0018/001897/189774e.pdf [accessed October 2013].


[19] Pelkonen, P., Hakkila, P., Karjalainen, T. & Schlamadinger, B. (2000), Woody biomass as an energy source challenges in Europe, European Forest Institute, pp. 7378.

[20] White, E. M. (2010), Woody biomass for bioenergy and biofuels in the United States a briefing paper, General Technical Report PNW-GTR-825. US Department of Agriculture, Forest Service, Pacific Northwest Research Station, Portland, US.

[21] International Institute for Applied Systems Analysis (IIASA)/Food and Agriculture Organization of the United Nations (FAO) (2010), Global agro-ecological zones (GAEZ v3.0). IIASA, Laxenburg and FAO, Rome. Available from: http://www.fao.org/nr/gaez/en/# [accessed February 2014].

[22] WorldBank.org, Water resource management. Available from: http://water.worldbank.org/topics/agricultural-water-management [accessed July 2013].

[23] Siebert, S. et al. (2010), Groundwater use for irrigation a global inventory, Hydrology and Earth System Sciences, vol. 14, no. 10, pp. 186380.

[24] Portmann, F.T., Siebert, S. & Dll, P. (2010), MIRCA2000Global monthly irrigated and rainfed crop areas around the year 2000: a new high-resolution data set for agricultural and hydrological modeling, Global Biogeochemical Cycles, vol. 24, no. 1.

[25] Curmi, E., Richards, K., Fenner, R., Allwood, J.A., Kopec, G. & Bajzelj, B. (2013), An integrated representation of the services provided by global water resources, Journal of Environmental Management, vol. 129, pp. 456462.

[26] Williams, E.D. & Simmons, J.E. (2013), Water in the energy industry: an introduction. BP, London, UK.

[27] van Velthuizen, H. et al. (2006), Mapping biophysical factors that influence agricultural production and rural vulnerability, Environmental and Natural Resources, series 11. FAO & IIASA, Rome.

Land is often classified according to potential use for agriculture. Broader climatic and ecosystem classifications are also used. Both systems are useful in considering which crops to grow and where to grow them.

Agriculture involves a series of operations to produce crops, and modern techniques are highly mechanized. Understanding the energy needs and GHG emissions of these processes is important for understanding whether growing biomass crops will be economic and energy efficient at a particular site.

Different plants employ different methods for utilizing carbon dioxide and water, allowing for plant growth under a wide range of conditions. The way in which each type of plant grows and develops affects its productivity and its potential yield.

Various raw materials derived from plants including sugars, starch, cellulose, lignin and oils are used in energy production. The physical properties and chemical complexity of these materials affect the ease and energy efficiency of processing them into biofuels.

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2 Important concepts | 23

2 Important concepts

Global ecosystems and land classifications Land is commonly classified according to its actual or potential use for agriculture, and this is sometimes described as land capability classes. In the context of this handbook, however, where we review wide-ranging biomass crops (both potential and realized), we look at land more holistically because land not normally prioritized for agricultural use can sometimes support carefully selected biomass crops. Traditional land classification takes into account soil type, previous land use, fertility, water availability, potential for erosion and accessibility for agriculture. These remain important indicators of land that might support bioenergy production. Productivity

and sustainability of production will depend on these land characteristics, together with management and crop choice.

Land areas can be categorized by grouping ecosystems that have similar climatic, biotic and abiotic conditions. Each such group constitutes a biome, and different biomes give rise to different types of use biomes are described more fully in Chapter 5. Figure 2.1 summarizes the global areas of different biomes, the types of feedstock or existing vegetation, and their carbon productivity and end uses. In short, the diagram connects biomes to the various services they provide [1].

Understanding bioenergy production systems requires background knowledge in many diverse fields. This chapter sets out some of the fundamental concepts. There is also a comprehensive glossary at the end of this handbook.

Tropical forests

Temperate forests

Boreal forestsCropland residual

Grasslands

Shrublands

Losses

Livestock respiration

Food waste

Potential natural vegetation [M km2 ]

Slice 1Land productivity[Pg C/y]

Final services[Pg C/y]

Slice 2 Slice 4Slice 3 Slice 5Actual land use [M km2 ]

Slice 6Harvesting[Pg C/y]

Modifications[Pg C/y]

Fire

[3.7]Livestock feed

Food [0.8]

Fuel [1.2]

Fibre [0.6]

[4.5]

[47.0]

ECOSYSTEM

SERVICES

Heterotrophicrespiration

Unit conversionarea to carbon

NPP0 loss

Pasture [28.1]

Cropland[15.0]

Unmanageddryland [14.8]

Forest[42.4]

Built-up [0.7]

Tundra and desert[28.9]

Tropical forests

Temperate forests

Boreal forests

Savanna

Grassland/steppe

Dense shrubland

Open shrubland

Tundra

Desert, polar desertRock/ice

[22.6]

[24.5]

[8.2]

[19.2]

[14.3]

[6.0]

[11.9]

[15.3]

[8.2]

NPP0 loss

NPP0 loss

[12.2Pg C/y]

[6.0Pg C/y]

[7.2Pg C/y]

[30.5Pg C/y]

[1.4Pg C/y ]

Crop harvest

[2.2]Wood harvest

[1.8]Grazed biomass

Meat

Fire

Waste assim.

Pollination

Pest control

Air quality

Water cycling

Water quality

Flood control

Erosion control

Soil formation

Nutrient cycling

Recreation

Scientific value

[0.84]

[1.8]

Carbon sink [2.6]

NPP0 loss

Losses

[1.1]

[1.8]

720 gC/m2

400gC/m

430gC/m

490gC/m

50gC/m

2

2

2

2

stock1530Pg C

stock80Pg C

stock310Pg C

stock220Pg C

Figure 2.1Sankey diagram showing global biomes, vegetation, carbon productivity and end uses[2]. There are a number of nomenclatures currently used for biomes and those listed on the left represent a slightly modified classification by Ramankutty and Foley[1]. The left-hand column, slice 1, shows areas of potential natural vegetation, while slice 2 shows actual land use after appropriation for human use. Slice 3 shows land productivity in Petagrams or Pg (billion tonnes) of carbon per year and also the amount of carbon stored in these lands in Pg. The final three slices show how this carbon moves through harvesting and processing to final services. Also shown are losses to net primary productivity (NPP0) attributed to lower productivity on conversion from natural vegetation. Food, fibre and fuel account for only a small amount of final use. The majority of fixed carbon is available for use by other species, is ultimately respired (heterotrophic respiration) and contributes to a variety of services, collectively called ecosystem services. The vertical width of each bar in the diagram is proportional to the area of land use or the amount of carbon per annum associated with a particular segment[3].

24 | 2 Important concepts

One can see that more than a third of land has been actively transformed from its natural state to cropland, pasture and built-up areas. Cropland and pasture are found in several biomes, and most crop production is harvested every year. While crop productivity can be quite high, there are numerous routes for losses in productivity due to disease, fire, nutrient and climatic variability during harvest and even waste after harvest. These losses, and the relatively high fraction of harvest that goes to the relatively energy-inefficient production of livestock, results in only a very small fraction of the total productivity providing food, fuel and fibre. Otherwise unattributed production is allocated to various worldwide ecosystems.

There are disagreements in the literature as to how land types should be classified. Nomenclature varies by country and according to intended purpose. As a result, there are no internationally standardized definitions of land types and the quality of land-use data varies between countries. Land considered by some to be abandoned may actually be used informally for fuel and grazing. Some even conclude that no land is really available, as any choice in using land for a different purpose will ultimately affect the current use and output of that land, regardless of whether that use is deliberate. Despite these caveats, it is nevertheless useful to have a sense of the different land types and the terminology used to describe their potential productivity.

Land types

The US Department of Agriculture (USDA) describes eight land classes, based on soil types rated according to their relative ability to support common agricultural crops[4]. These are tempered by four sub-categories that recognize topographic problems that may limit production, including waterlogging, shallowness of the soil, erodibility and climatic limitation (such as extreme cold). The following categories condense these classes (and similar classifications by other national agricultural services) into five categories. These are not mutually exclusive: specific sites may fit one or more of these five categories.

Prime

Prime land can produce the highest yields of major commodity crops with proper agronomic management. It is easily accessed and cultivated, and is well suited to a range of crops, including food, feed, forage, fibre and oilseed. Despite its great potential, incorrect management (using techniques that reduce soil organic content or allow wind or water erosion) of prime land can degrade productivity. Prime agricultural land is usually rainfed, rather than irrigated, but irrigation can allow access to good soils climatically limited by inadequate rainfall. In this case, careful management is necessary to avoid excess salt deposition or exhaustion of water sources.

Marginal

Marginal land gives lower yields of annual grain crops than prime land, or has only limited potential for agricultural production. It may also be fertile land that is susceptible to erosion. Even though soil quality may be high, for example, cultivation of such soil on steep slopes can cause rapid soil loss unless terraces are economically feasible. Land that is marginal for conventional row-crop agriculture might support high yields of biomass crops: sloping land may support perennial bioenergy feedstocks (given sufficient water) while minimizing the risk of erosion relative to other land uses. Low productivity pasture, supporting one to two head of cattle per hectare, may also be in this category. In Brazil, with appropriate amelioration of soil nutrient deficiencies, such land supports significant yields of sugarcane.

Degraded

Degraded land can support only low productivity of conventional commodity crops. Degradation is usually the consequence of intensive management, usually associated with agricultural or forestry practices that result in the loss of organic matter, the production of laterites (hard, clay-like materials) in tropical soils, and actual loss of bulk soil by water or wind erosion. The dustbowl of the southern central US, where cultivation led to serious wind erosion, is a classic example. Such land, however, may provide viable yields of deep-rooted crops that bind the soil and have the potential to restore soil carbon. Land may also be degraded by excessive salt deposition through irrigation with low-quality water or pollution with industrial effluents or mining wastes. In some cases, land degradation is so severe that further agricultural use with traditional crops is not possible and the land is abandoned.

Abandoned

Land may be abandoned for various reasons, such as increasingly unreliable rainfall, competition from higher production elsewhere, or a collapse of local markets. In the eastern coastal states of the US, for example, much production became uneconomic following the Civil War, while the better soils of the mid-western US began to deliver grain at lower prices, making production progressively more uneconomic in the north. As a result much land in the eastern US has dropped out of cultivation in the past 150 years. This pattern of loss continues to this day. More recently, increasingly productive agriculture and the break-up of collective farms in Eastern Europe have resulted in abandonment.

Land previously used for crops or pasture is classified as abandoned if it is now unused and has not been converted to forest or urban use. If the period of abandonment has been short, such land may be converted back to agricultural use with relatively low economic and environmental cost. Long-abandoned land can, however, through the process of ecological succession, become host to diverse plant and animal communities. Re-established native communities often store large amounts of carbon (both in soils and above-ground biomass) and may also provide valuable ecosystem services such as protection of water catchment areas, wildlife conservation and recreation.

2 Important concepts | 25

Agricultural inputs and practices

Agriculture involves management that varies according to crop species, soil conditions, climate, topography and culture. Some of the most common practices for cultivating crops are explained below.

Tillage

Tillage is the preparation of land to receive crops, and is practised in many forms. For annual crops, it must be done every year (unless reduced or zero-tillage methods, as described below, are used). Traditionally, it involves turning the soil with a plough to bury weeds or crop residues, followed by harrowing to produce the fine tilth necessary for good seed germination. It is a major activity in agriculture, requiring either considerable labour or mechanization (with its concomitant cost in GHG emissions). Mechanized tillage has enabled huge increases in productivity by increasing the speed of ground preparation and by allowing more land to come under cultivation.

Tillage improves the conditions of certain soils unfavourable for agricultural production and is effective in helping to control annual weeds, but if used improperly can cause serious land degradation (erosion). Reduced- or zero-tillage methods, where seed is sown (using direct-drilling equipment) into unploughed land that has been cleared (by hand or using herbicides), are widely used to reduce cost, maintain soil carbon levels and reduce erosion. Many perennial bioenergy crops (such as sugarcane a

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ESC Biomass Handbook