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Thursday, January 10, 2013

Eskom mulls big biomass co-firing plan in bid to lower coal emissions



South Africa’s State-owned electricity utility Eskom is considering an ambitious plan to begin burning biomass alongside coal at some of its power stations, as part of a strategy aimed at lowering the group’s sizeable carbon foot- print.

In 2011/12, the coal-heavy utility produced a material 231.9-million tons of carbon dioxide emissions, while burning 125.21-million tons of coal and selling 224 785 GWh of electricity.

Nevertheless, the group has set an objective of reducing its relative emissions between now and 2025 and its absolute emissions by 10% against the existing baseline over the longer term.

To do so, various projects are being pursued, including the 100 MW Sere wind farm, in the Western Cape, a 100 MW con- centrating solar thermal project, in the Northern Cape, as well as the installation of photovoltaic plants alongside some of its existing coal-fired power station sites.

Also included in the mix, however, is a possible large-scale biomass co-firing initiative, which Eskom estimates has the potential to displace about 10% of its yearly coal consumption with ‘torrefied’ wood pellets.

Biomass is considered a ‘carbon-neutral’ fuel because the carbon dioxide released during the burning of the fuel is recaptured from the atmosphere when new plants are grown. However, there are additional greenhouse-gas emissions generated in the processing and transportation of the biomass material.

Eskom is specifically interested in refined pellets, as the fuel is more coal-like in its characteristics when compared with untreated biomass, which typically cannot be stored outside in the coal yard because of a tendency to absorb moisture and leach organic compounds. There is also a significant threat of self-ignition.

The plan, which is based on employing waste wood material, is being pursued as something of a ‘public–public partnership’, involving several State-owned companies (SoCs). Besides Eskom, the project could involve State forestry group Safcol, the Industrial Development Corporation (IDC) and freight logistics group Transnet.

This cross-SoC approach is viewed as a critical success factor, as the venture’s success or failure will depend as much on Eskom’s offer of security of demand as it will on an efficient logistics plan and the ability to secure the required feedstock.

The proposal is reportedly receiving high-level support from within government, which views the initiative as an opportunity to create new rural employment opportunities, while potentially stimulating the creation of a new agro-industry.

Regional Project?
The project’s regional-integration potential – premised on the fact that South Africa alone does not have a sufficiently large forest resource to supply Eskom’s biomass needs – is also significant.

It is estimated that, for Eskom to displace 10%, or nearly 13-million tons of coal volumes with biomass, it will have to secure 20-million tons yearly of raw wood waste.

“South Africa alone would not be able to satisfy that demand,” Eskom divisional executive responsible for technology Matshela Koko tells Engineering News.

Supplementary sources will, therefore, have to be secured in the rest of Southern Africa, including from Safcol’s envisaged plantings in the Mozambique operation under what is dubbed ‘Ifloma Phase 2’.

A Council for Scientific and Industrial Research study, commissioned by Eskom, shows that South African forestry residues could feasibly only supply about three-million tons of the required raw material yearly.

“Therein also lies the logistical difficulties,” Koko adds, highlighting the possible importance of Transnet’s role.

Logistics aside, Eskom is also concerned about the potential of the projects to displace land that would otherwise have been available for food production, with plantations dedicated to supplying fuel for electricity.

To address this concern, Koko reports that the group is in the process of commissioning a study through the United Nations Food and Agriculture Organisation (FAO) to analyse the potential food-security impact of a large-scale co-firing project.

The FAO study, which will analyse the 1.6-million hectares across Southern Africa deemed necessary to sustain a 20-million-ton-a-year supply chain, should help provide more clarity on the possible food-versus-fuel threats and what actions should be taken to mitigate them.

However, if the biomass can be secured in a way that does not undermine the long-term food-fuel dynamic, Eskom believes an entirely new industry could emerge to process the wood into ‘black pellets’.

The utility has started engaging with potential technology providers to settle on the most appropriate technology for its and South Africa’s needs.

The model being proposed is for Eskom to provide the security of demand needed for the creation of large-scale biomass production and processing to justify the logistics and materials handling investment that will be required.

Black Pellets
Currently envisaged is co-firing using torrefied black pellets and Eskom is engaging with eight possible technology providers on possible solutions.

These technology companies are mostly based in Europe and North America, but Koko says the aim is to select a technology option for the initial pilot phase that could eventually be fully localised.

Torrefaction, which gives biomass more coal-like properties, involves heating the material at temperatures of between 240 ˚C and 320 ˚C in the absence of oxygen.

During the process, the moisture and unwanted fibrous components are removed, while most of the energy is retained.

Koko tells Engineering News that the relatively mature 2 400 MW Arnot power station has already been selected for a pilot co-firing phase, based on forestry residue material sourced from Safcol forests in Mpumalanga.

Boiler engineering manager Yokesh Singh estimates that 130 000 t/y of raw biomass will have to be secured to produce 60 000 t/y of torrefied product for the pilot at Arnot.

He also estimates that the black pellets are likely to cost about R2 000/t once the necessary investments have been made to facilitate the necessary refining and logistics.

The initial material is likely to be sourced from Safcol, which has confirmed that it is in discussions with Eskom and the IDC on the co-firing project, while it continues to consider cogeneration options in remote areas, such as Timbadola and Entabeni, in Limpopo.

Eskom is targeting material from the tops and limbs of the trees, which is typically left in the field to bio-degrade to enrich the soil. Even if the co-firing venture proceeds, at least 10% of the material will have to be left behind to provide such nutrients.

Safcol does not currently classify the material as waste, owing to its soil-enriching qualities. Nevertheless, the company tells Engineering News that it is considering various ways to produce and collect biomass, including supplying sawdust, bark and chips.

“Pulp logs are ideally suited to this purpose, which are obtained when our thinning and harvesting operations take place,” senior manager: corporate communication and liaisonLeslie Mudimeli says.

The Safcol material could initially be processed at a pelletising facility near Sabie, in Mpumalanga, which is currently on care and maintenance after a previous investment failed.

Co-Firing Pilot
Arnot has been selected partly for its proximity to the wood source and partly because it is one of Eskom’s stations that has been struggling to secure the requisite quality of coal. This has resulted in the plant performing relatively poorly when compared with the rest of the utility’s 13-strong coal fleet.

Eskom estimates that an investment of about R300-million will be required at the Arnot site to enable the station to store, handle and burn the black pellets.

The capital costs associated with the upstream refining and necessary logistical systems are yet to be fully determined. It is also not clear whether SoC, Eskom, Safcol, or the IDC will play the lead investment role.

If all goes according to plan, the pilot phase could receive Eskom board sanction early in 2013. Safcol, meanwhile, confirms that it will take part in and support the pilot, but says it is unable to “give any details at this stage on the project”.

Koko reports the initial analysis shows biomass co-firing to be competitive, compared with other renewable energy solutions, such as wind, solar and small hydro.

The utility has also completed a technology study and went on a roadshow in October to meet eight possible providers, short-listed through a market assessment conducted by an international consulting company.

But there are several other outstanding issues that also have to be dealt with before the project proceeds.

Firstly, biomass co-firing is not an option reflected in South Africa’s current Integrated Resource Plan.

Secondly, a funding plan will also have to be finalised, with Eskom having to consider whether such a project should be pursued as a strategic venture, as is the case with its wind and solar projects, and funded separately, or whether it should be blended into its tariff application.

Koko is convinced the plan has merit from a cost, emission reduction, rural development, industrialisation and regional integration perspective. What is needed, however, is a “success story”, which he hopes the Arnot pilot will provide.

“I hope that, by the first quarter of 2013, we will be in a position to move ahead with the pilot phase,” Koko concludes.

1 comment:

Krista Hiles said...

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