Blog

Back

Biogas for Brazil

16.01.2019

Deborah Sacks, Waste and Resources Specialist, Department for International Trade (DIT UK)

The advantages of biogas are numerous and varied. This makes it difficult to explain them all, even to others in the world of energy. There are three different benefits to biogas production:

·         the proper management of waste organic material;

·         the production that can be used for energy production or transport fuel; and

·         the creation of a fertiliser from the solid material generated (digestate).

Organic material will decompose naturally and produce carbon dioxide. If waste material is sent to a landfill site it may decompose anaerobically and produce methane instead. It there is a high level of organic material in waste sent for incineration, the waste will be too wet to burn and will need to be dried out. So, the most environmentally sustainable approach is to use anaerobic digestion (AD) to capture these greenhouse gases that are produced through decomposition and use them as a substitute for fossil fuels.

Importantly, this means that organic wastes, when are properly managed, may not fill up more landfill sites. In addition, a digestate is produced as the other main output which can be spread on land as a fertiliser, reducing the need for expensive chemical fertilisers. AD also produces a liquid residue known as a leachate. This must be treated before it is allowed to enter rivers or the groundwater in order to remove fertilisers and other chemicals that may have been in the original material and prevent too many nutrients reaching the wider environment.

Biogas in the UK is generated in anaerobic digestion facilities from agricultural wastes as well as waste food. When crops are grown for biogas production, there are strict rules to ensure that good agricultural land is retained for growing food and to prevent it being used for fuel crops.

While the total amount of arable land used for bioenergy crops in the UK has increased in recent years, it currently equates to 2.2% of the total arable area. Crops grown specifically for biogas in the UK include maize, miscanthus, sugar beet and short rotation coppice (small poplar or willow trees).

A popular feedstock for AD in the UK is food waste, either from households or the food industry, including food processing, sandwich and ready-meal production and restaurants. This food waste needs to be collected separately and kept free from contamination, although de-packaging techniques are now very effective. Food waste must also be brought to a temperature of at least 60°C for 2 days in order to get rid of any pathogens.

The methane is then cleaned and injected into the national grid for gas, or used to generate electricity in engines on site. A growing use for biogas is also transport since it is a clean fuel for heavy vehicles.

One or the advantages of biogas is that it can be produced in remote areas that are not connected to either the gas or electricity grids. Biogas can be produced on farms using animal or crop wastes for use in processing the crops on site or stored and transported as required. However, the gas does need to be cleaned and stored correctly and safely.

In the UK different incentive regimes are applied to the generation of biogas depending on its final use. The biogas producer must decide which subsidy is best for their purposes:

a)      Renewable electricity is subsidised through a system called “Contracts for Difference” through which electricity generators bid through an auction mechanism for the amount that they will be paid per unit generated.

b)      The Renewable Heat Incentive is a subsidy per unit of heat generated from biomethane injection. Applications must be made through a Government Agency and regular reports submitted on how much biomethane is generated.

c)      Biomethane used for transport is subsided through the Renewable Transport Fuel Obligation which is managed by the Department for Transport.

The generation of biogas is an important technology with huge advantages for both the environment and for communities that otherwise have difficulty accessing energy. However, the technology does need to be carefully managed and the necessary skills must be developed in order to grow the industry.

Categorias: Blog

LATEST POSTS