Southern African Energy Efficiency Convention (SAEEC2011)

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DRIEFONTEIN RENEWABLE ENERGY PROJECT Karolina Euler-van Hulst, AB van der Merwe Promethium Carbon, Bryanston Johannesburg

ABSTRACT This paper sets out the findings of a pre-feasibility study on a renewable energy project, conducted by Promethium Carbon, at the Gold Fields Driefontein Mine. The aim is to identify and quantify possible biomass and waste sources at the Driefontein mine, and propose technologies for renewable energy generation. A first pass financial evaluation of the conceptual project design was also included. The study objective is to achieve a triple bottom-line; energy security, social benefits, and environmental benefits, while ensuring that the project is financially viable. Biomass sources identified include on-site alien vegetation and other mining waste streams. An on-site energy plantation was proposed as an additional feedstock stream, and evaluated in terms of land availability, water availability, and the viability of certain indigenous species. Various thermal conversion technology process routes were assessed for technical and financial viability. Carbon credit eligibility was also considered for this project at a feasibility level. 1. INTRODUCTION

A prefeasibility study was conducted by Promethium Carbon, on contract of Gold Fields, for a renewable energy project at the Gold Fields Driefontein Mine. The project has a number of objectives: • Energy Security: The provision of Eskom

independent power on the mine will contribute to the energy security of the mine. The energy security of the project has two components to it. The first is to provide a source of power that is not dependant on the Eskom grid. The second is to provide power that is shielded from the expected Eskom price increases.

• Economic viability: The project must yield an acceptable IRR for the money invested.

• Sustainable Development: The sustainable development benefits of the project impacts on a number of issues: • Establishment of a profitable business on the

mine premises that will continue after mine closure

• Job creation after mine closure • The possibility to extract value from the water

pumping, through the use of the water in irrigation during and after the life of the mine.

• If it is decided to keep pumping water after life of mine to avoid Acid Mine Drainage (other technologies might become available to deal with AMD), to supply electricity for this pumping.

• Assistance in the implementation of the EMPR for mine closure

• The possibility of phyto-remediation on areas of the mine property that may be contaminated.

• Offer a solution to the Driefontein solid waste disposal problem.

• Greenhouse Gas Mitigation:

The project could earn carbon credits in a number of ways: • The displacement of Eskom electricity can earn

in the order of 1 ton of CO2 equivalent per MWh generated. These credits can be earned under the Clean Development Mechanism (CDM) of the Kyoto Protocol.

• The planting of energy crops could earn afforestation credits, either under the CDM or under a voluntary standard such as the VCS.

• The project could further impact on the ability to earn voluntary carbon credits for other projects under the VCS scheme.

This report sets out the findings of the first phase of the project: it entails the technical aspects of the proposed project on a pre-feasibility level, and the carbon credit issues on a feasibility level.

2. SITE SPECIFIC INFORMATION

Driefontein is situated ~70 km west of Johannesburg, at latitude 26°24’S and longitude 27°30’E, near Carletonville in the Gauteng Province of South Africa. Geologically, the mine is located on the North Western Rim of the Witwatersrand Basin.

Driefontein Mine owns in the order of 10,000 ha. Land availability at the mine for the establishment of an energy plantation will be based on the following sustainability criteria:

• To preserve sensitive landscapes and geological features;

• To maintain the diversity and composition of habitats, and the indigenous plants and animals therein;

• Exclude land currently used for living, industrial activities, roads, landfills, etc.

Several of the vegetation area units available at Driefontein are unsuitable for energy crops; i.e. harvesting and transportation will be difficult on ridges and pans. The types of vegetation that can be transformed to energy plantations were determined based on the suitability and sustainability criteria.

2.1 LAND AVAILABILITY

The disturbed grasslands in the North are qualified to be of medium-low biodiversity significance and, except for

Southern African Energy Efficiency Convention (SAEEC2011)

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some hinder from tailings impoundments, seem to be fully available for energy plantations. About 350 ha within the disturbed grasslands are still used for agricultural purposes. Since Gold Fields is in the process of buying this land back from farmers, it is assumed that it will also become available for energy plantations. Based on this information, it is assumed that the areas described in Figure 1 will be available, following compliance with the sustainability criteria, for the energy plantation.

Table 1: Land availability for energy plantation establishment at Driefontein

Description Available Area (ha)

Disturbed Grasslands + agricultural land within the disturbed grasslands

1,490+350

30% of the Natural Grasslands 1,003 Total 2,843

3. IDENTIFIED FUEL SOURCES

The proposed project will convert biomass to energy from a number of sources. The sources of fuel could include waste from surface and underground, as well as biomass from alien eradication and from the harvesting of sustainable energy plantations from areas undergoing phyto-remediation.

The following fuel sources have been investigated on availability, quality and costs in the pre-feasibility study:

- Alien invader species on the Driefontein property; - Potential of an sustainable energy plantation; and - Other biomass waste sources.

3.1 ALIEN VEGETATION

The woody alien vegetation cover within the supplied study boundary was mapped at approximately 1185 hectares [1]. The most abundant woody species are Acacia Mearnsii (black wattle), Sesbania punicea (a shrub) and Eucalyptus Camaldulensis. It is suggested that the black wattle and eucalyptus found around mine tailings should be maintained (harvested but not eliminated) as it serves as a vegetation buffer to reduce contaminated water leakage from the tailings. Furthermore, these established trees provide a visual screen. Though it is suggested that harvesting should be conducted in stages (not all trees around the mine tailing should be harvested at the same time to assure water level stability), these trees can be cut back to a stump height of 5-10 cm, after which the trees will re-grow. In this case, permits should be obtained from the Department of Water Affairs, seedlings must be removed, and indigenous trees should be planted around the alien trees to replace them once fully grown. Assuming that 25% of the area with woody alien vegetation is kept on locations such as the golf course, approximately 890 ha with alien vegetation is available for harvest. The alien vegetation density is not known. Assuming an average cover of 50% and a yield of

123 tonne/ha in the case of 100% cover, the total yield expected is approximately 55,000 tonne. 3.2. SUSTAINABLE ENERGY PLANTATION It is the project’s purpose to generate electricity. For this reason the sustainable energy plantation will grow either grasses or trees. Oil crops, such as Jatropha and Moringa, are usually used for bio-diesel production. Though bio-diesel could also be combusted in an engine to generate electricity, this conversion pathway is less efficient for the generation of electricity than combustion and pyrolysis technologies that make use of wood or grass. Perennial grasses and trees seem to be able to reach comparable yields. Forestry and energy crop experts who visited the Driefontein mine confirmed that tree as well as grass yields of approximately 12 to 15tDM/ha/yr are reasonable to expect using high yielding species. In the future, when soil fertility has been increased, and intensive cultivation is practiced (this includes irrigation), yields of up to 20tDM/ha/yr are expected to be possible. More research into indigenous perennial grasses suitable for the Driefontein area is required. Indigenous trees that are expected to perform well are indigenous Acacia species, Eucalyptus Camaldulensis, Combretum erythrophyllum (River bushwillow) and Celtis Africana (White stinkwood). Based on literature review, it is estimated that grasses can be cultivated and harvested for between 115-130 R/tonne dry matter (tDM), while trees are expected to be cultivated and harvested for between 165-175 R/tDM. Employment creation is expected to be higher in the case of cultivating trees than grasses as trees are more difficult to harvest. Grasses will fit in better with the natural landscape which is grasslands. Prioritization of the different advantages and disadvantages of both grasses and trees should be done by Gold Fields in the feasibility phase of the study. 3.3 OTHER WASTE SOURCES 3.3.1 Industrial and Municipal Solid Waste At Driefontein, industrial waste is gathered at each shaft and sorted for metal, plastic, timber, and paper and carton before it is transported by truck to the local municipality or recycling facility. Timber, paper, and carton can potentially be used for energy generation. Municipal solid waste and gardening waste from the local mining community will also add to the available fuel volumes. The amount of waste available as fuel in this project has been estimated as 10,000 m3 per year, which can contribute in the order of 1,500 tons per year (on a dry basis) renewable fuel. These will however decline as the end of the life of the mine is approached and the amount of workers on-site decrease.

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3.3.2 Sewage Sludge

The amount of sludge available as fuel in this project has been estimated as 2,800 m3 per year, which can contribute in the order of 150 tons per year (on a dry basis) renewable fuel. These low volumes dictate that the economics of collection and processing of this source must be carefully investigated before it is included in the project. 4. TECHNOLOGY REVIEW

4.1 PRE-TREATMENT

With the different sources of biomass and waste that will be generated in this project, pre-treatment is essential to ensure a constant uniform feed to the element process. For biomass collection manual extraction was chosen over mechanical extraction due to lower costs and more job creation. Pre-treatment methods considered for the biomass feed stream were chipping, grinding, pelletizing, and torrefaction (intermediate step). Equipment type and specifications largely depend on the feed particle size requirements for the specific thermal treatment. Therefore for the different technology routes modelled in the study, different configurations of chippers and grinders were considered. Pelletizing and torrefaction were not considered in the routes modelled, seeing as the biomass will be utilised onsite (no need for transport), and to reduce the cost of the overall process.

Due to the small municipal waste stream available at Driefontein, open table hand sorting and baling the accumulated recyclables will be used.

4.2 ELEMENT PROCESS

Three types of thermal treatment technologies were evaluated in this study: gasification, pyrolysis, and simple boiler and steam turbine setup. Among these technologies biofuel and biogas production was also considered, but deemed inadequate solutions for this study. Technology Advantage Disadvantage Gasification Largest electricity

generation and most energy efficient.

Highest capital cost

Pyrolysis Highest return on investment. Biochar can also be sold as a separate commodity which will help create jobs.

Lowest electrical energy efficiency due to biochar production.

Boiler and Steam Turbine

Lowest capital investment required.

Overall energy efficiency the lowest.

4.3 ENERGY RECOVERY

The type of energy recovery method used depends on the type of product stream obtained from the element process,

as well as the desired final product stream desired. The main energy demand at Driefontein is electricity. Electricity will either be generated via gas engines, or a boiler and steam turbine configuration, depending on the quality of the off-gas from the thermal process. Other options include: absorption chillers, which can help pre-cool water for the mine freezing plant, and biochar production from pyrolysis, which can be used to cultivate the new biomass plantation and aid in job creation and additional income for the project. On some of the thermal processes, additional waste heat recovery can be done, which can be used in an Organic Rankine Cycle (ORC) to generate extra electricity, or waste heat can also be used to heat water for communal showers.

5. PROCESS ROUTES MODELLED

Four process routes were modelled after careful consideration of the client requirement, associated costs, and environmental and social benefits:

1. Gasification with gas-engines for electricity generation;

2. Pyrolysis with biochar production and syngas burnt in a boiler and steam turbine set-up for electricity generation;

3. Pyrolysis with biochar production and syngas fed to absorption chillers;

4. Simple boiler and steam turbine setup for electricity generation.

All the process routes were modelled for trees and grasslands separately, as well as for different intercropping scenarios. The impact of equipment from different technology suppliers was also tested. Sensitivity analysis were conducted on the projects IRR to changes in biochar price, crop yield, capital cost, cultivation and harvesting cost, and intercropping scenario’s. Cash-flow analyses were also conducted for all the scenarios.

No active process simulation was conducted. All the models were static models, developed with data and costs obtained directly from technology suppliers. The level of detail was deemed sufficient for the requirements of Gold Fields at a pre-feasibility stage.

6. CARBON CREDITS

The project was evaluated for carbon credit eligibility under the Clean Development Mechanism (CDM) and the Verified Carbon Standard (VCS). Ultimately it was found that this project is eligible for carbon credits and will consist of two separate carbon credit projects for CDM or VCS registration, due to the applicability of different methodologies: • Sustainable energy farming

• CDM Afforestation project (AR-AM0005 - “Afforestation and reforestation project activities implemented for industrial and/or commercial uses” (version 4).), or

Southern African Energy Efficiency Convention (SAEEC2011)

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• VCS grasslands project (“Adoption of Sustainable Grassland Management through Adjustment of Fire and Grazing”)

• Electricity and thermal energy generation from renewable biomass and waste – CDM small scale project • If the project is developed as small scale project:

“Thermal energy production with or without electricity.” (AMS I.C. (Version 18).

• If the project is developed as a large scale project then no applicable methodology exists. A new methodology will have to be written based on the principles of AM0042 (Grid-connected electricity generation using biomass from newly developed dedicated plantations --- Version 2.0.1) and ACM0006 (Consolidated methodology for electricity and heat generation from biomass residues --- Version 11)

It was found that all the different process routes modelled were eligible for carbon credits, but with varying volumes of carbon dioxide savings. Different scenarios were modelled with and without carbon credits to determine economic viability of the project. 7. SUSTAINABLE DEVELOPMENT

As mentioned in the abstract, this project is justified for by, except its financial sustainability, a triple bottom line:

1- Energy security 2- Social benefits 3- Environmental benefits

7.1. ENERGY SECURITY

The rationale for the Driefontein co-generation project is based in part on the fact that electricity will remain in very short supply in South Africa for the foreseeable future. The country’s reserve margin has been under pressure since 2004. In 2008, Gold Fields experienced power cuts which made it necessary to suspend production because of the risk of miners being trapped underground. Apart from the incentives provided to energy intensive industries by the Demand Side Management programme, Eskom has also proposed to encourage demand-side savings by the introduction of a punitive tariff levied on users that exceed the limits allocated to them under the Power Conservation Programme (“PCP”). The PCP has not been implemented, but specific discussions have been held with the Energy-intensive User Group in this regard. Independent power production will address both the risk of power cuts, as well as being penalized under the Power Conservation Programme.

7.2. SOCIAL BENEFITS

Multiple social benefits are expected to be generated via the proposed renewable energy project. Especially important is the fact that multiple of these social benefits will support local, employment providing communities,

during the time that the mine will be downscaling towards end of life of mine.

7.2.1. Employment

As can be seen in Figure 2, Gold Fields employees are expected to decrease over time while coming closer to the end of life of mine.

Figure 2: Estimated permanent employee figures for future life of mine Renewable energy technologies are in general more labour intensive than conventional energy technologies and bio-energy has the highest employment-creation potential1. The proposed biomass and waste to electricity project will create employment at a time that the mine reduces its amount of employees. Direct jobs will be created in waste collection and separation, during the establishment, management and harvesting of energy plantations and during the transportation, processing and feeding of biomass into the energy conversion technology of choice. Indirect jobs could be created through, for example, the establishment of a nursery for the supply of trees or grasses of choice.

7.2.2. Fuel Supply

Current fuel use by the local communities is mainly wood (including wood from the underground mining operations), paraffin and coal. The proposed project could manufacture wood briquettes and supply the local communities with cleaner energy sources. This could be done in combination with support schemes to obtain health friendly stoves. Before such a programme can be initiated, wood will have to be analyzed for possible contamination, which could cause a health hazard when burned2.

7.2.3. Reduced vulnerability

Local communities are vulnerable to mine induced soil and water contamination. Contamination in the soil can be taken up by trees and food crops and cause harm when

1 ECOTEC, 1999. The impact of renewables on employment and economic growth. EC Project initiated by EUFORES and coordinated by ECOTEC Research and Consulting Ltd, ALTENER Project 4.1030/E/97-009. 2 An evaluation of South African fuelwood with regards to calorific value and environmental impact. Francis Munalula, Martina Meincken, biomass and bioenergy 33 (2009)

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burned as fuel wood in an open fire or consumed. The proposed project looks at phytoremediation of soil and water and therefore will improve the surroundings of the local communities.

7.2.4. Skills development

Local community members will be trained to be able to manage the energy plantation. An additional benefit will be the development of skills which, once the mining land is fully rehabilitated, can be used for the cultivation of other crops.

7.3. ENVIRONMENTAL BENEFITS 7.3.1. Land Rehabilitation

The impact of mining operations on the Witwatersrand basin has been investigated by [2] and [3]. It was found that ‘contamination of soil was severe, could extent for hundreds of metres from the mine residue deposits (slimes dumps), and had resulted in significant increases in soil acidity, salinity and heavy metal availability to plants and impairment of nutrient cycling’. Overall, [2] estimated that 6,000 km2 of soils are significantly impacted by gold mining in this region.

It is expected that the Driefontein land is (partly) polluted and will require land rehabilitation before it can be used for any other purposes. For that reason, the energy plantation will be established using plants with a phytoremediation3 capacity. Harvested trees and grasses will be combusted, after which heavy metals can be extracted from the flue gas and land filled.

7.3.2. Greenhouse gas emissions reductions

With South Africa making the voluntary commitment of 34% carbon emission reductions by 2020, and the imminent national carbon tax, reducing carbon emissions is as much an environmental issue as it is a financial decision.

This project will reduce greenhouse gas emissions by substituting grid electricity (largely coal based) for on-site generated power from renewable biomass and other industrial and municipal wastes obtainable at the Driefontein mining site.

8. CONCLUSIONS

The following main conclusions could be drawn based on the finding of the study; • When applying good cultivation practices, an annual

yield of approximately 30,000 tonne of biomass per year is expected.

3 Phytoremediation is the use of plants to partially or substantially remediate selected contaminants in contaminated soil, sludge, sediment, ground water, surface water and waste water3.

• Other onsite waste sources could contribute approximately 2,500 tonne per year.

• Of all the energy generation models evaluated, pyrolysis appears to be economically the most viable, though this is very dependent on the sale and market price of biochar; • All the models evaluated are eligible for CERs,

seeing as applicable methodologies are available for CDM registration and financial additionality can be proven;

• Additional benefits of the project would be land rehabilitation, job creation and increased energy security.

9. REFERENCES

[1] Abell. S: Personal Communication (Natural Scientific Services), Aug 2010.

[2] Weiersbye, I.M., Witkowski, E.T.F.: “The structure, diversity and persistence of naturally-colonizing and introduced vegetation on gold tailings and tailings-polluted soils.”, Plant Ecology & Conservation Series, No. 8, Anglogold Ltd., 1998, pp. 224.

[3] Weiersbye, I.M., Witkowski, E.T.F., and Reichardt,

M.T.: “The flora of gold and uranium tailings dams, and tailings-polluted soils, of South Africa’s deep-level mines.”, Bothalia, No. 36, Vol. 1, 2006, pp. 101-127.

10. AUTHORS

Principal Author: Karolina Euler – van Hulst holds a Masters degree in Sustainable Development, with a focus on renewable energy, from Utrecht University in the Netherlands. At present she is a Carbon Advisor with Promethium Carbon. Co-author: AB van der Merwe holds Master of Science

degree in Process Engineering from the University of Stellenbosch. He is presently a Carbon Advisor at Promethium Carbon.