AD 'the missing link' for bioenergy

Opinion piece by Rosaline Hulse of the Anaerobic Digestion and Biogas Association (ADBA):

The UK has to meet ambitious targets to increase the amount of energy produced from renewable sources. As a result the demand for bioenergy and biofuels is estimated to double in the coming years. In order to meet this growing demand the UK will have to build a suitable infrastructure and develop process and practice that meet demand whilst keeping in line with climate change targets.

Achieving sustainable intensification in farming is therefore a high priority. This is crucial not only to farmers looking to maximise outputs and minimise risk in their business, but also so that UK farming can become part of the UK energy mix and help to provide both food and energy security.

The ability of anaerobic digestion (AD) to help diversify and intensify a farming business whilst reducing its environmental impact is central to both sustainable intensification and our bioenergy goals.

In the UK the focus of attention on AD is often around waste feedstocks, where we are likely to be a market leader. However, purpose grown crops (PGCs) for AD plants (an established and mature industry in Germany) also have an important role to play in delivering the UK’s bioenergy targets.

The anaerobic digestion of PGCs is often described as a biomass technology although it differs significantly from other forms of biomass energy in terms of cultivation, process and sustainability. These differences largely come from the way that AD can easily be integrated into farming practice, rather than being separated from it.

PGCs can be - and already are - grown as break crops helping to promote biodiversity in British agriculture, complementing existing agricultural rotations and improving soil quality. The land used to grow PGCs does not need to be moved completely away from food production.

On farms with carefully planned rotations, biodiversity can be aided by introducing a wider range of crops in the rotation with different characteristics (such as planting, flowering and harvest dates).

Maize is the most commonly used PGC for AD at present, largely due to the conditions in Germany, but technological advances and the local climate mean that a wider range of crops, including grasses and wild flower mixes could be used in the UK.

AD offers many benefits to farms, including producing a renewable energy - which can be used to reduce bills for electricity, heat and transport or sold into the grid - and a biofertiliser, in the form of ‘digestate’ which recycles nutrients back to land. Farmers benefit economically from diversified revenue from energy generated on site and potential markets for biofertiliser.