Chapter 4 Module 9Environmental systems analysis methodology

Can totally different sanitation systems be fairly compared?How are environmental impacts measured?

Life cycle assessment (LCA)

• Aim– Evaluate environmental

burdens of a product or service

– Using a cradle-to-grave perspective

• from raw material extraction to waste management and final disposal.

Raw material acquisition

Processes

Transport

Manufacture

Use

Waste management

LCA work with an expanded system

• Comparison require delivery of similar product– That leave you with compared system – And compensatory system (external system)

Compared system Compensatory system

Product

Waste sources

Waste managementsystem

Emissions

Energy Fertiliser

Material

Energy

Energy Fertiliser

Costs

Compensatory system

Alternativeproductionof energy

AlternativeproductionofN-,P-fertiliser

System boundary

Alternativeenergy raw

material

Alternativefertiliser raw

material

Example of a system comparison

Source: Jan-Olov Sundquist, IVL

Functional unit, valued products

Core system incinerationWaste

Heat

Power

Functional unit

Core system LandfillWaste

Heat

Power

Heat production

Power production

Compensatory or external system

Functional unit

Resources – Energy and materials Water Land

Impacts on human health (toxicological and non-toxicological impacts, excluding and including work environment)

Global warming Depletion of stratospheric ozoneAcidificationEutrophicationPhoto-oxidant formationEco-toxicological impactsHabitat alterations and impacts on biological diversity

Impact categories to be considered in an LCA

Title

Collection and aggregation of data

NOx

NH3

P

etc.

CO2

CH4

N2O

Eutrophication

Global warming

Index

Inventory Characterisation Weighting

Which environmental effect is most important?

• Global vs local• Long-term vs short-term

• Importance of the impact– Compare the system impact with total national

emissions

Weighting of global warming

Global Warming Potentials (GWP) as CO2 –equivalents for different trace gases and time-frames (IPCC, 2001) Trace gas GWP, 20 years GWP, 100 years GWP, 500 years Carbon dioxide, CO2 1 1 1 Methane, CH4 62 23 7 Nitrous oxide, N2O 275 296 156

Weighing of acidification

Weighting factors for acidification for two scenarios, min and max (Lindfors et al., 1995). Substance Min [mol H+/g] Max [mol H+/g] SO2 0.031 0.031 HCl 0.027 0.027 NOx 0 0.022 NH3 0 0.059

Weighting of eutrophicationWeighting factors for eutrophication

Substance Maximum (g O2 per g) Minimum (g O2 per g) N to air 20 NOx to air 6 NH3 to air 19.8 3.8 N to water 20 NO3 to water 4,4 NH4 to water 18.6 3.6 P to water 140 140 PO4

3- 46 46 COD 1 1

Remember…

It is a great difference between potential and actual environmental impacts.