Energy Recovery from Waste
One of the most exciting developments in recent years has been how we are beginning to find new and more innovative ways of getting energy from our waste. This developing technology is not only being used to lower the running costs of our industries and agricultural businesses but can also be utilised on a much bigger scale as cities such as Sheffield have shown.
The development of energy recovery from waste has gone hand in hand with our desire to be more energy efficient and make the most of all our resources. Sustainability is the name of the game and could solve the problem of what to do with our non-recyclable waste in the meantime.
Creating energy from our rubbish is usually termed a waste to energy (WtE) or energy from Waste (EfW) process and involves generating either heat or electricity, and often a mixture of both, through a variety of technologies.
In the history of waste management, you have to go way back to the turn of the 19th century to find the first incinerator being used but it is only reasonably recently that we have begun to look at ways of utilising this process for better energy efficiency. The burning of waste can be used to boil water for use in factories and other industrial settings but it can often produce noxious by-products. With developments that prevent harmful gases being released into the atmosphere, this form of recycling our waste is something that many commercial businesses have incorporated into their operating infrastructure, providing greater efficiency in the process.
There are several ways in which waste can be used to produce energy:
- Incineration: the burning of waste which reduces it to about 20 to 30% residue.
- Gasification: heating to high temperatures to convert organic or fossil fuels to carbon monoxide, hydrogen and CO2.
- Pyrolysis: heating materials at high temperature in the absence of oxygen.
- Anaerobic Digestion: the natural breakdown of organic material using bacteria in the absence of oxygen.
The key is to get the recyclable components of any waste out in the first instance and reuse them and then burn what is left to produce energy. It sounds simple but developers have struggled with issues such as harmful gas production, the logistics of particular waste types and the amount of investment that has been needed to push energy recovery from waste forward.
The Review of Waste Policy in England which was published in 2011 stipulated that using solutions such as landfill was to be considered a last resort from now on and has led to more focus on getting energy from waste in the future. One such solution has been developed in Sheffield and could be replicated across the UK.
Sheffield Energy Recovery Facility
One area where waste management has taken a more proactive approach is in the north east city of Sheffield. Their energy recovery facility on the outskirts of the city is designed to turn household and commercial waste, which would have been destined for landfill, into electricity and heat for the local community. It can handle up to nearly quarter of a million tonnes of waste a year and generates around 21 MW of electricity which is enough to provide power to 25,000 homes. The site also produces 46 MW of heat that is supplied to 140 buildings that are connected to the facility.
In truth, Sheffield has been at the forefront of trying to recover energy from waste since the 1970s and the Energy Recovery Facility that opened in 2007 is simply the latest part of this innovative approach.
How Does it Work?
Waste from the local community, including businesses and homes, is delivered to the site and poured into a storage facility which can hold up to 2,700 tonnes of waste at a time. An overhead crane then lifts the waste onto a hopper and this feeds into the incinerator unit that operates at a temperature of 850 °C. Above this unit is a large boiler that produces steam, which in turn operates a turbine to create electricity for the national grid, as well as providing hot water for the local community. Various safety measures are used to reduce the emission of substances such as oxide of nitrogen and particulates (dust) so that only clean gases are released into the atmosphere.
Developments such as this could revolutionise waste management methods in the UK and across the world, providing a semi-renewable way of developing energy and reducing the amount of rubbish we have sitting in large areas such as landfills.
One area where converting waste is becoming more widespread is on farms who are utilising anaerobic digestion to deal with agricultural waste. This involves the breakdown of organic matter by microorganisms which produces two useful by products: biogas for use in heating and highly concentrated fertilizer for use on fields.
Energy recovery from waste is certainly beginning to become a more viable proposition and could help solve the perennial problem of what we do with large amounts of rubbish that we can’t recycle or reuse.
Find out about the different types of waste here.