Previously published in CIWM magazine. Energy policy has been high on the agenda lately. The publication of the Energy White Paper will make public the level of the government’s commitment to sustainable energy sources and its determination to reduce greenhouse gas emissions.

Waste treatment increasingly incorporates energy generation, with resultant carbon emissions. The waste and the energy markets therefore, cannot be considered independently as they are integrally linked.

168 million tonnes of waste was deposited at waste management facilities permitted by the Environment Agency in England and Wales in 2004-5. In the same period 106 million tonnes of waste was treated or disposed of in these regions. 72% of this went to landfill, 21% to treatment and 7% was incinerated. A further 58 million tonnes of waste was handled by transfer facilities and metal recycling sites.

Landfill inputs have fallen gradually since 1998-9 while the amount of waste handled by treatment facilities and incinerators has almost doubled.

Local authorities have to decide how best to manage the residual waste that remains after recycling and composting in order to meet future landfill diversion targets. There are a number of issues affecting the choice of waste management technology including landfill costs & taxes, pre-treatment requirements, the waste strategy review, the climate change agenda, energy prices, public perception and acceptability. The importance of these issues is changing but the Landfill Allowance Trading Scheme (LATS) remains to be the current main driver.

According to the Landfill Directive, by 2020, biodegradable municipal waste going to landfills must be reduced to 35% of the total amount of the base year 1995, reducing greenhouse gas emissions by around 74 million tonnes CO₂-equivalent.

Methane emissions from landfills are much more potent as a greenhouse gas than CO₂. From a climate change perspective greenhouse gas (GHG) emissions should therefore be the most important concern when choosing a waste management technology.

Energy-from-waste (EfW) facilities are seen as an effective method by which LATS obligations can be met. Indeed EfW is being regarded by most stakeholders in the waste management supply chain as the solution for LATS compliance. In its literal sense, EfW covers a wide range of technologies varying by the type of thermal conversion or energy recovery. The choice of technology determines the energy conversion and ultimately the efficiency achieved. However we must not forget other alternatives like anaerobic digestion and the carbon sequestration potential of stabilised mechanical biological treatment (MBT) process outputs.

In 1999 a study for the Department of Trade and Industry concluded that incineration offers little or no advantage over gas-fired power stations in terms of carbon emissions. Therefore the assumption made by some energy providers and policy makers that EfW is good for the climate is not accurate. Comparison should be made between the options in terms of MWh of electricity generated per tonne of CO2 emitted into the atmosphere.

Looking at it in this way, some facilities clearly outperform straight incineration achieving more MWh per tonne of CO₂ emitted to the atmosphere. A good example of efficient energy recovery from waste is the Zabalgarbi plant located in the Basque Country in Spain. The project incorporates a new concept for generation of electricity from MSW in which the steam generated from the boiler is reheated by the gas turbine exhaust achieving over 40% energy efficiency compared to 24% in conventional plants.

From all the waste treatment options, EfW within an integrated solution could play an important role. From the energy point of view there are huge benefits to the embedded generation potential of small to medium sized EfW facilities. However, it is imperative that we look at the most efficient processes and make sure that the heat from the facility is used by neighbouring developments.

Looking at the processes in every aspect of life, we waste more heat than we use. Around half is wasted or evaporated to the atmosphere. However, we still consume energy to generate heat both in industry and our homes. Combined Heat and Power (CHP) is the simultaneous generation of heat and power in a single process and provides one of the most cost-effective approaches for reducing CO₂ emissions.

CHP puts to use the heat that is normally wasted to the environment. CHP can increase the overall efficiency of fuel use to more than 75%, compared with around 50% from conventional electricity generation. Furthermore, because it often supplies electricity locally, CHP can also avoid transmission and distribution losses. Another way to make use of the heat is through district heating (DH).

The basic idea of DH is to use heat resources that would otherwise be wasted to satisfy local customer heat demand. The heat is distributed through a network of pipes, which connects the source with the customer. In order to make a DH system competitive it is imperative to guaranty a suitable cheap heat source and a demand of heat from the market. The source and the customer have to be local in order to minimise the capital investment in the distribution network. Suitable heat demands include space heating, hot water in residential, public and commercial buildings and low-temperature industrial heat demands.

District heating is extensively used in other countries. Denmark for instance has the political motivation and legislation to make it viable and it provides 60% of space heating. The sole example of a district-heating scheme supplied by EfW in the UK is in Sheffield. This plant utilises 115,000 tonnes of waste to produce 36MW of thermal energy and up to 6.8MW electrical energy, saving the emission of 15,105 tonnes of CO2 in 2004.

District heating, in combination with CHP, can produce heat and electricity with an overall efficiency of 85-90% of the input fuel.

We need to understand that renewable energy is not only renewable electricity, but includes heat as well. Policies in general need to encourage building owners, developers, construction companies and engineering companies to invest. In particular we need to integrate the waste management industry with all of these parties. There is a need for change in behaviour. A strategy that encourages low-carbon and renewable heating and cooling could help the waste industry to release the potential contained in our waste.

Sadly anaerobic digestion was not included in the review of the waste strategy. Anaerobic digestion is a proven technology that is widely utilised in continental Europe.

Anaerobic digestion has a huge potential to efficiently release the energy contained in putrescible wastes. A recent report by Waste Resources Action Programme estimated that 477-761 GWh per annum could be generated if food waste was digested. To put it in perspective this is the energy used by between 103,000-164,000 households.

Partnerships are essential to achieving the successful implementation of improved infrastructure in the municipal waste sector. The choice of treatment technology should be linked directly with the type of waste stream that is present. Anaerobic digestion is highly suited to the treatment of food waste rich feedstocks and other putrescible wastes. It is less suitable for treating green and woody waste, which is less readily degradable. Municipal and commercial waste streams could be more optimally treated together, rather than as separate entities. This would reduce the number of facilities needed and provide a more sustainable solution with associated economies of scale.

Waste-to-energy plants are an essential part of both the waste management and the energy supply network. They could contribute to security of energy supply and provide solutions for UK and EU waste management. Efforts should be made to ensure that the potential energy embedded in waste materials is recovered in the most efficient way. In the current climate it should not be acceptable to treat waste without due consideration of the climate change consequences