The WTE market is currently growing rapidly around the world. While it has traditionally been a mature and slow-growing market, a perfect storm of fears about pollution, the impact of climate change and the growing focus on finding non-fossil fuel sources of energy, has meant a renewed focus on the opportunities available.
There have been concerns raised about WTE. Namely that using waste for fuel can encourage wastefulness and discourage recycling, and that there are harmful by-products of the transformation of waste to energy, including toxins and greenhouse gases. Yet new, cleaner technologies developed over the last few years can often avoid the generation of such by-products providing an effectively carbon neutral process.
There are a number of issues for developers in selecting a new technology: the efficiency of the process itself, the reliability and lifetime of the waste feedstock, local environmental impact in terms of by-products, as well as planning and consumer and media opinion. Some technologies provide only part of the process. For example, mechanical biological treatment (MBT) or autoclaving treats and sorts residual waste, resulting in streams of recyclable materials, organic materials (often suitable for composting), other materials suitable for use as refuse-derived fuel (RDF) and other inert materials. However, as part solutions to the waste issue, they do leave some fractions of waste for landfill and the resultant RDF is frequently used in straightforward incineration.Today’s technology
A number of new market technologies, such as anaerobic digestion, pyrolysis and gasification, are in the process of being deployed. These technologies provide the potential to recover products from the waste stream which complete incineration would not allow and a significant proportion are focusing on biomass waste. Pyrolysis involves heating waste in the absence of oxygen at very high temperatures, which breaks down complex molecules and resultant gases are then passed into a combustion chamber where they are heated (in the presence of oxygen) at temperatures around 1250°C. The process produces liquid oil which is used as a fuel, as well as gases that can be used to run steam turbines, and chars. Gasification can be used with a far broader range of feedstock, and simply involves heating wastes in a low-oxygen atmosphere to produce a synthetic gas, which can then be used to power a steam turbine.
With the advent of wider usage of technologies, the crucial questions are scalability and the cost-effectiveness of each technology. One of the reasons for the success of incineration is the lack of IP required to develop a plant this makes it simpler and relatively cheaper than some of the more technically advanced forms of WTE for waste management companies and local government to implement. Yet improvements in the technologies, especially increasing efficiencies with new catalysts and enzymes around improving bioreaction and pyrolysis technologies are beginning to make an impact on the cost.
Another crucial requirement for the successful development of waste-to-energy plants is to secure a sufficiently robust waste stream and, to a great extent, different forms of technology will be appropriate to one of a number of different waste sources.
Operationally, incinerators are reasonably immune to variable input characteristics (they’ll burn most things) but they are vulnerable to feedstock changes. They may lose energy content if, for example, plastic packaging disappeared over the long term.
Landfill gas to energy has proved popular, especially given that the dominant gas emitted from landfill, methane, has a global warming potential 23 times that of carbon dioxide. However, the growing concern about the pollutant impact of landfill means that there will be far less landfill available in the future, which is likely to have a dramatic impact on its role as an energy generator. This is an additional problem with incineration, since ash residues from the process can be as high as 25% by volume, most of it can go nowhere but to landfill. Chars resulting from the pyrolysis process, for example when using rubber waste such as tyres, may also generate toxins and require landfilling.
The necessary footprint of MSW incineration sites can also cause problems. The majority of waste management and incineration sites have a large footprint, with waste being trucked in from the surrounding region. Such plants can have high operating and capital costs, requiring long payback times, which can expose them to a higher risk of waste stream content changes. The large scale of such plants can make the power generated easier to integrate into existing grid networks but low efficiencies mean that large quantities of waste may need to be trucked in from the surrounding regions. And that need for large waste streams causes concern regarding the impact on local waste reduction or recycling streams.Economies of scale
It is the large-scale nature of such waste management programmes that is beginning to be questioned. There is a growing demand for locally generated power, and an even stronger demand for local waste solutions. Not only is there an accepted need to reduce the amount of waste that our economies generate, but the logistical requirements for large scale waste transportation have a significant carbon impact another increasing concern to industry and government. If the energy from waste market is going to grow, it’s important to be able to deliver plants with a small footprint, that can generate efficient power and heat for a local district or industrial area, and that have an ongoing and reliable fuel source. This will not only contribute to renewable energy targets, but also counter many arguments which result in planning opposition.
Scale model made for a potential 100,000 tonnage plant Click here to enlarge image
One of the key things that needs to be resolved is how to finance such new infrastructure. Few of the existing large waste management players have the capacity, the finance or the technologies to meet all the new waste targets on their own, let alone those likely to be enforced in the next few years. New technologies and new ways of financing necessary facilities do exist however, with new businesses and project financiers eager to follow the success of the wind market with the waste and waste to energy market.
Traditional large scale incineration has been relatively easy to fund, as the capital costs are clear, the technology well known, and the revenue stream (through gate fees from local or regional governments) easy to ascertain. This makes them appealing to traditional public, project and debt finance. With many of the new technologies, investors can be concerned about long term revenues, as there are few plants that have been up and running for a long time, and many governments prefer centralized solutions operated by businesses with large resources. This puts pressure on small scale developers they can’t bid for large scale waste management contracts on the same terms as the established industry players. This in turn can deter equity investors, and make it problematic to raise either debt or equity funding.
Yet they can also have significant advantages over large scale waste management solutions, financially and environmentally. Smaller plants generate fewer waste miles and certain new technologies do not face issues with the leachate and toxic fly ash so frequently associated with incineration. They’re also cheaper to build and can be scaled up as needed. As they are usually privately financed, local government need not take on any capital expenditure the plants are financed on the basis of agreed revenue-bearing contracts such as gate fees for MSW.One solution: Gasplasma
An effective WTE plant should be able to generate a number of revenue streams: gate fees for the waste it receives, generated electricity which is sold to the local grid on long-term power purchase agreements, and potential revenue from the sale of recyclables removed or the sale of heat to co-located industries. This approach is of growing interest to the major European energy providers, who must boost their renewable electricity output 15%-20% to meet the targets. With commercial waste predicted to increase by 50% by 2020, the ability to build small plants in industrial areas could transform the energy landscape with local waste being used to produce local electricity.
Plasmarok, a valuable by-product of the Gasplasma process Click here to enlarge image
One example of this is Advanced Plasma Power’s Gasplasma process, which combines two well-established technologies, fluid bed gasification and plasma arc conversion. APP’s original parent company Tetronics uses plasma successfully in 33 sites around the world, in vitrifying incinerator bottom ash and hazardous waste, as well as in metals recovery. Gasification has been well proven in a number of markets from coal to biomass. Aside from the initial power supply from the local electrical grid, the whole process is self-sustaining after the initial electrical charge is used. It is environmentally friendly, and it produces materials that have commercial applications and thus can generate further profit.
A model of how a full scale APP plant would look Click here to enlarge image
An average 100,000 tonne APP plant could generate six steady revenue streams from each site: gate fees for the waste it receives; the sale of all recyclables removed; the electricity generated (which is sold to the local grid on long-term power purchase agreement); the heat sold to industries that co-locate on the same site; double ROCS under the UK Renewable Obligation scheme; and the sale of the glassy material, Plasmarok, which is produced by the process and can provide a return as it is sold as building material or aggregate. A plant would generate 11.5 MW of electricity, using 4.5 MW to run the plant, with the remaining 7 MW exported to the local grid. This is enough for over 12,000 homes. With heat recovery, the process is over 65% efficient.
Even better, for those authorities’ conscious of the need to cut their carbon footprints its carbon contribution to the environment is virtually nil. Analysis of the APP process has been shown to have a ‘negative’ carbon footprint in comparison to other forms of energy generation, produce virtually zero emissions and has the highest landfill diversion rate of any available technology, making it very attractive to local authorities.
While plasma technology has been in use for many years it has only recently been developed as a waste management solution. This was partly because the conventional landfill approach was considerably less expensive, even with transportation costs and gate fees, and there was no regulated requirement for low-carbon energy. However, with increasing landfill diversion targets and renewable energy targets, the relative cost of the technology has been transformed. This is making plasma gasification one of the most potentially exciting opportunities in the sector.The waste-energy partnership
There is no question that the energy mix of the global economy is in flux, and we are going to see an increasingly broad range of solutions, ranging from fuel cells to the implementation of a hydrogen economy. A great deal of work is currently being undertaken at the cutting edge of technology in developing flexible or multi-purpose fuels, and billions of dollars are being invested to bring these opportunities to market.
Post-sorted waste (recyclables removed, dried and shredded) travelling up the conveyer belt to the gasifier Click here to enlarge image
Until those technologies become widely available, we must accelerate our implementation of those technologies which work today. Energy and waste policy are not correlated anywhere in the world, but there is a significant amount of energy stored in waste and that is increasingly being recognized in a resource-constrained world. Perhaps we need to accept that the waste and energy industries cannot, and should not, be managed as separate entities. The process of managing our waste, water and energy requirements must be re-thought.
Felicia Jackson, Associate, Carbon International. Carbon International is a specialist communications company focused exclusively on the environmental sector.