How rubbish in the tank could slash fleet carbon emissions

BusinessGreen.com: How do you go about producing vehicle fuel from what is essentially rubbish?
James Ingall: The technology has just been launched and will be used at Surrey's largest landfill site, which contains mainly domestic waste mixed with some commercial and industrial waste. To be able to liquefy landfill gas, you first have to compress it and then remove the impurities, such as the hydrogen sulphide and sulphur dioxide that can damage the engines. You then need to pull out the nitrogen and carbon dioxide, because CO2 will solidify if it is chilled and nitrogen is non-condensable. Once that process is completed the gas is liquefied through chilling.

How efficient is the process?
Energy efficiency-wise, the process has a broad parameter of three-and-a-half to one. So for every unit of energy we use, we get about three-and-a half-units back.

How much gas will be produced?
5,000 tons of LBM (liquid biomethane) will be produced annually for 10 to 15 years.

What will the gas be used for and when will it be available?
LBM will be used as vehicle fuel for commercial operators such as waste management fleets or large logistic businesses. It is particularly suitable for firms operating in urban environments because it is very clean-burning and quiet, meaning vehicles using the biofuel will benefit from emissions reduction and noise reduction. As such, it is perfect for the intercity environment and ideal for night-time deliveries. Used in some vehicles it can avoid the congestion charge, too.

What are the advantages of using LBM?
Unlike most biofuels, LBM is derived from waste, which is readily available in commercial quantities. There is no threat to food crops, unlike with other biofuel feedstocks, and rubbish is not used to supply any other industry so there is no competition. Biofuel produced from tallow, for example, was thought to be sustainable, but it competes with the soap and detergent industries that need it for producing their goods. In contrast, rubbish is as sustainable as it gets.

LBM is also more than 96 per cent pure methane so there are no high-end hydrocarbons in the mix which can cause pre-ignition and knocking in the engine. It is a better quality and denser fuel than natural gas.

What are the environmental benefits of LBM compared to other fuels?
There is a 70 per cent CO2 reduction compared to diesel and petrol. In addition, LBM has a lower carbon density compared with most other biofuels. The carbon savings delivered by different biofuels are listed on the government's Renewable Transport Fuel Obligation web site, where people have to provide data about the sustainability credentials and carbon savings from different biofuels. Compared with ethanol from sugar cane and corn, as well as biodiesel derived from rapeseed oil or palm oil, biomethane actually has one of the lowest carbon intensities. There are about 27 to 35 grams of carbon per megajoule of energy in LBM, whereas diesel has about 85 to 86 grams and crop-derived biofuels are somewhere in between. Some of those biofuels even have carbon content as high as 60 grams per meg joule and are therefore more carbon intensive than people may think.

James Ingall is finance director at UK-based biomethane producer Gasrec