London rubbish could generate electricity for two million homes

(09/11/2009)

A new report from the London Assembly reveals that London’s rubbish could be used to generate electricity for up to two million homes and heat for up to 625,000 homes. The capital produces about 22 million tonnes of waste per year, including enough waste thrown out by Londoners to fill Canary Wharf tower every eight days. Most of this waste is taken outside of London and buried in landfill sites, but this is no longer sustainable.

The Assembly Environment Committee report, ‘Where there’s muck there’s brass’, says it is time London had an alternative strategy for managing its non-recyclable waste – in the form of waste to energy conversion.

Converting London’s non-recyclable waste to energy and heat – through non-thermal technology, anaerobic digestion, mechanical biological treatment or thermal technologies including pyrolysis and gasification – has clear environmental benefits:
· It is estimated London’s CO2 could be reduced by 1.2 million tonnes, helping the Mayor meet his 2025 target of reducing emissions by 60 percent.
· Waste sent to landfill will be significantly reduced.
· Energy produced from these new technologies is renewable and helps achieve the central government target of 15 per cent renewable energy by 2020.

Murad Qureshi AM, Chair of the London Assembly Environment Committee, said: “London’s waste management is unsustainable and uneconomical. The Mayor must take the lead on further measures to help jump-start waste management step change.

“Waste to energy technology will help the capital reduce greenhouse gases, cut down on waste sent to landfill, increase renewable energy generation, benefit the economy and create jobs. Our recommendations are pragmatic and short-term and will contribute to a rapid roll-out of these very exciting technologies that turn waste into a useful and valuable commodity.”

The report highlights a number of barriers preventing the widespread use of non-incineration waste to energy technologies and priorities for Mayoral action, including:

Contracts: Long-term existing contracts for treatment of municipal waste make it difficult for potential companies to obtain waste material. To address this, the report calls on the London Waste Recycling Board (LWaRB) to provide details on all borough contracts and give advice on how to generate waste streams to support new plants.

Difficulties obtaining planning consent: The Mayor should co-ordinate the development of effective and cost-efficient waste to energy infrastructure.

Public Opposition: The LWaRB should ensure Londoners are fully informed of the facts and benefits of non-incineration waste to energy plants.

The Committee acknowledges two significant areas for concern: potential health impacts caused by air pollution and the dangers of reducing recycling rates. The Committee calls on the Mayor to publish evidence on climate impacts and health effects of each waste to energy technology.

Non-thermal: Aerobic and anaerobic digestion (AD) is a method of processing wet biological waste (food, sewage) capturing methane which can be used to generate power and heat and producing compost. Bacteria break down organic matter in the absence of oxygen (anaerobic) or with oxygen (aerobic) to produce biogas. This can be used as a renewable energy source, both for heat and power. Alternatively, the carbon dioxide and other impurities can be removed to produce biomethane which can be used as a transport fuel or injected into the gas grid. The treated material (or digestate) can be used as a fertiliser and soil conditioner.

Mechanical Biological Treatment (MBT) involves two treatments: stage one mechanical sorting which involves shredding, screening and extraction to separate the oversized recyclables and biodegradable waste. A second stage applies to the biological waste fraction, where microbial activity breaks down the waste within a controlled and monitored environment. MBT is seen as a pre-sort to other thermal technologies.

Advanced Thermal Treatment (ATT) technologies are in their infancy in the UK, but some commercial scale plants are in operation in Europe, North America and Japan and include: Gasification: material is heated to a high temperature (600 – 1200 degrees centigrade) with oxygen. A char residue plus synthetic gas is produced (syngas) typically methane, carbon monoxide and hydrogen. This syngas can be used to produce heat, fuel for gas engines / turbines or for liquid fuel production. The first gasification plant in London will be the Biossence plant in East London, for which construction is due to start in the next five years.

Pyrolysis involves indirect heating of the waste (400 – 1200 degrees centigrade) in an oxygen-free atmosphere. It produces char, tar and oils and a hydrocarbon gas. The organic material is converted into gases, which can be burnt to produce heat and electricity.

Related categories:  Biodegradable waste   Biofuels and biomass   Eco-friendly Power generation   Environmental technologies for Residential and Green homes