February 18, 2009 It’s common knowledge that the majority of electricity generation and waste disposal methods currently in widespread use are not very environmentally friendly. New British venture Waste2tricity aims to kill two environmentally damaging birds with one stone by taking carbon based waste, either municipal solid waste (MSW) or waste from business and industry, and converting it into clean electricity, thereby reducing the amount of rubbish going to landfill and potentially making a significant contribution to the UK electricity supply.
The system involves sorted carbon waste, including plastics, paper, cardboard, food and other plant material, entering a plasma gasification chamber and being turned into syngas by the application of very high temperatures (+6000°C). This process has advantages over incineration, which has not been adopted on a large scale for the conversion of MSW into power because of the low efficiency, fears over emissions and waste from incineration or from existing gasification systems. Compared to incineration systems the Waste2tricity system produces fewer pollutant gases, tar, ash and fly ash and the main by-product, vitrified slag, is inert and can be used as road-building aggregates, with the added benefit of reducing demand for gravel extraction.
Waste2Tricity will develop the process in two stages. In Stage 1 the cleaned syngas will be fed into an internal combustion engine (ICE) generator, with an average generation efficiency of about 30%. In Stage 2, the syngas will be processed and converted to hydrogen and the ICEs will be replaced by new generation alkaline fuel cells, which have the highest conversion efficiency of hydrogen to electricity of any process. By the combination of plasma gasification with fuel cells Waste2tricity claims the net output of electricity to the UK National Grid could increase by over 50% compared to existing technologies and that the new generation fuel cells will increase the net output of electricity by a minimum of 60% over an internal combustion engine generation system or by 130% over a steam turbine system. Waste2Tricity also estimates that the cost of generating electricity can be less than UKP3p (USD$0.04cents) per KWh at today's prices.
The environmental benefits of the Waste2Tricity system include:
- a reduction in landfill and therefore reduction of emissions of greenhouse gases such as methane from that source
a plasma gasification plant using new generation fuel cells will not cause a net increase in atmospheric CO2 as it bypasses the highly potent methane phase of the natural carbon cycle
The company is currently in negotiation to secure the agreement of a number of strategic partners to proceed with its first 50,000 tonne pilot plant, representing Stage One of its program and recently secured an exclusive UK agreement with AFC Energy plc for the supply of alkaline fuel cells to be integrated into Stage Two of the program when the ICE will be replaced with AFC Energy fuel cells. Waste2tricity says the AFC fuel cell will have a far lower manufacturing carbon footprint than existing rare earth substrates, and stored electricity becomes 'portable' without the need for expensive grid investment. Waste2tricity says the Stage One plant could be ready within three years with Stage Two in operation in four to five years and they estimate that around 22,500 homes could be powered by one plant.
There is approximately 35-40 million tonnes of biomass sent to landfill in the UK each year, of which Waste2Tricity believes it could initially process around 20%, which would be capable of generating around 2,100 kWh of electricity from every tonne of waste currently sent to landfill. By using waste with a short-cycle biogenic composition, electricity generated by the Waste2Tricity process will help electricity suppliers meet the Renewables Obligation, which requires UK power suppliers to derive a specified proportion of the electricity they supply to their customers from renewables. This started at 3% in 2003, rising gradually to 10.4% by 2010, and 15.4% by 2015 so electricity suppliers in the UK, not to mention around the world, are sure to be keeping a close eye on Waste2tricity’s progress.
Darren Quick
