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The benefits of plasma gasification

Plasma gasification is one of the technologies leading us into the future. Here, we look at the rise of PG and its status around the world, plus learn more about a new process which turns scrap carbon into energy using plasma gasification and alkaline fuel cells

by Peter Jones

Figure 1. Diagram of the plasma gasification process

Consider three factors occurring on a global scale: a looming energy gap, an overwhelming need for zero carbon waste technologies, and ambitious 2020 emissions targets. With landfill availability declining within three years due to rising gate fees, there is a need to find alternative treatments for MSW. The calorific value of waste is also important. MSW is of interest to power companies who want to continue supplying heat, electricity and hydrogen or fuel gases using environmentally-friendly technology.

One British venture, Waste2Tricity, has a mission to convert scrap carbon into energy (SCIE) using the most efficient energy conversion process available – implementing a unique combination of proven plasma assisted gasification (PG) technology with new generation alkaline fuel cells.

2020 emissions targets

We are currently at a crossroads. Familiar phrases including 'low carbon energy' and 'emission reduction pledges' form the news agenda. With 2020 fast approaching, the four regions of the world expected to emit almost two thirds of the carbon between now and 2050 are under tremendous pressure. India has pledged to curb the carbon emitted relative to the growth of its economy – its carbon intensity – by 24%, while China may cut its carbon intensity by more than 40%. The EU has pledged a 20% cut in carbon emissions, and the US 17%.

The recent Copenhagen climate change conference failed to find a solution to the problem. With the attention of the world's media on it for two weeks, negotiations ended in a weak political agreement that has no legal standing and does not force any country to reduce emissions. With power stations going off-line and higher landfill taxes in effect, more low carbon commercial technologies are needed if we are to meet 2020 emission targets.

Gasification and fuel cells – an unbeatable combination?

Already a commonly-used technology in the chemical, fertilizer, and coal-to-liquids industries, gasification applications are becoming increasingly diverse. The electricity/power industry has benefited from gasification technology for over 35 years. The waste-to-energy (WTE) industry is also realising the environmental and economic benefits of gasification and is increasingly attracting attention as a potential solution to challenges surrounding renewable energy and reducing landfill capacities.

The Mihama-Mikata facility has an input of 24 tonnes per day.

Enabling the recovery of available energy from low value materials like municipal solid waste (MSW), gasification technology can change waste disposal from an environmental headache into a commercially viable proposition. WTE provides an interesting option for large retail energy users in so far as they can improve security of supply via a co-located facility whilst reducing cost of energy in parallel. It has the potential to increase the amount of renewable electricity generated globally, reduce environmental impacts as well as reduce waste disposal costs.

With some nations consuming more than others, the quality and quantity of waste varies across borders. And so does the way it is managed. Yet only two MSW plasma-based systems already operate commercially, with plans afoot for a large new plant in the US. The company supplying plasma gasification systems for all these facilities is Westinghouse Plasma Corporation (WPC), owned by Alter NRG, and considered the world leader in PG.

These two plants are both in Japan, built by Hitachi Metals, Ltd., and have processed MSW using WPC plasma gasification technology since 2002. The largest facility, located in Utashinai, was constructed in 2002 and became fully operational in 2003, processing a 220 tonnes per day mixture of auto shredder residue and MSW to produce electricity. The second facility near the neighbouring cities of Mihama and Mikata, treats 20 tonnes per day of MSW and four tonnes per day of sewage sludge for the production of heat utilized in a municipal waste water treatment facility and was commissioned in 2002. WPC also has two other projects in the pipeline in New Orleans and Minnesota.

Spurred by volatile oil and natural gas prices, and more stringent environmental regulations, it is generally acknowledged that CO₂ management will be a stricter requirement in future energy production. As an existing clean energy technology that is flexible and reliable, worldwide gasification capacity is projected to grow 70% by 2015.

So why then, has the conversion of MSW into power yet to be adopted on a large scale? Up until now, landfill tipping fees have been so low that it has been cheaper to simply bury waste. Due to high initial capital costs, there have also traditionally been concerns over low efficiency, emissions and waste from MSW incineration or from gasification systems. This said, however, proper economic consideration needs to be taken to ensure that plasma gasification plants established for municipalities do not end up costing them more than landfill tipping fees.

A strong business case

An exclusive UK sales agreement with Alter NRG, and exclusive rights to new generation alkaline fuels cells under development by AFC Energy plc, provide Waste2Tricity with a distinct advantage in the UK market. Alter NRG's technology is ideal for producing a hydrogen stream, from waste and other low value feedstocks, which is suitable as fuel for AFC's technology. AFC has completed initial field trials at AkzoNobel's chlor–alkali plant in Bitterfeld, Germany. Alkaline fuel cell technology is the best-known fuel cell technology today, and is even used by NASA.

Waste2Tricity's use of alkaline fuel cells is projected to increase the net output of electricity by a minimum of 60% over an ICE (internal combustion engine) and by over 130% for a steam turbine. This will result in the most efficient and economic means of converting scrap carbon into energy, generating 2100 kWh of electricity from every tonne of MSW currently sent to landfill. Waste2Tricity estimates that the cost of generating electricity could be less than 3p per KWh (at today's prices.

Challenges ahead for plasma gasification

All over the world, plasma gasification technology could make the disposal of waste commercially viable and increase the amount of renewable electricity. Local laws and planning issues are the main hurdles to be overcome and are often influenced by the capacity of the proposed plant. However, there are ways to make developments more acceptable, such as building them on existing landfill sites, and utilizing existing infrastructure such as roads built for waste transport.

It all depends, however, on whether local authorities have the budget to convert existing incineration plants into WTE plants, using technologies such as plasma gasification and fuel cells.

In a global financial climate emerging from recession, funding is a major hurdle. But WTE using plasma gasification can be commercially viable and profitable, especially when compared to other renewables such as wind, hydro/wave, geothermal and solar/photovoltaic which are gridlocked in competition for subsidies and venture capital. These renewables cost around £3.5million per installed MWe capacity, which is less profitable when compared with plasma gasification.

The issues with funding and new technologies revolve around the conservative position taken by the waste companies which is only now starting to 'loosen up' as the reality of a low carbon economy starts to become apparent. Traditionally, waste companies in countries such as the UK have been wedded to landfill and mass burn as service offerings and as a consequence are reluctant to invest in innovation until it is well proven. Landfill on the other hand is a proven solution, taking just about anything. This resistance to adoption of new technologies reflects in the bankability of any emerging technology.

This situation is exacerbated enormously by the liquidity crisis. Although venture capital funding in equity remains firm for the 'right' projects, with cash-generating asset backed opportunities, non revenue, not fully-demonstrated technologies have received almost zero investment. Government investment schemes have been largely ineffectual, either requiring matching funds or other hurdles that make the monies inaccessible.

Increasing levels of recycling and composting could reduce the carbon content of waste, reducing convertible energy per tonne. But PG works hand in hand with physical segregation of specialist material streams for recycling because it can accept suitably-dried material containing all forms of carbon-based content. Due to cross contamination, much useful material is rendered valueless for recycling, so the advice remains to reduce, re-use, recycle and compost as much as possible, but whatever waste is left over can and should be utilized for WTE.

The rise of PG will help educate the public about WTE and SCIE plants. This, and other new technologies, combined with strict emission monitoring by legislation, allow us to recover energy from waste, reduce landfill, produce energy and lower CO₂ emissions. If we are ever to fully harness the benefits of WTE, governments must now accept the fact that energy and waste are connected.

Peter Jones is a director of Waste2Tricity
e-mail: ecolateraljones@btinternet.com

Waste2Tricity was established to implement the most efficient energy conversion process available using a unique combination of new generation alkaline fuel cells alongside plasma gasification and other existing proven technologies.

The Waste2Tricity Process

Waste2Tricity obtains a homogenized waste stream, either in conjunction with an existing waste management company, allowing the installation to be established on an existing site, or from a commercial customer, such as a supermarket chain that back hauls its waste to a central depot. Ideally, the mix comprises 35% organics, 35% paper and cardboard, 25% plastic and 5% other materials.

Using plasma torches in an oxygen-starved environment, very high temperatures of 5000°C+ decompose the waste into very simple molecules, which comes out as a syngas composed of only hydrogen, carbon monoxide and a small amount of carbon dioxide. In contrast to direct combustion, the plasma gasification process emits fewer pollutant gases, and no bottom ash. Harmful particles, such as dioxins, are destroyed in the process. The main by-product – inert vitrified slag – can be used as road-building aggregates, reducing demand for gravel extraction. As well as these advantages, plasma gasification has potentially the lowest CO₂ impact per tonne of waste used of any of these technologies.

The syngas from plasma gasification can be used to fuel an internal combustion engine, or a gas turbine, either of which generate more electricity from a given quantity of waste than can be achieved by a conventional steam cycle. Taking a further innovative step forward, new UK venture Waste2Tricity will combine plasma gasification with new generation fuel cells, potentially increasing the net output of electricity by 60% over an internal combustion engine generation system, or by 130% over a steam cycle system.