KWS

Biogas Cropping Needs More Careful Consideration For Long Term Success

July 2012

Farmers growing crops for biogas need to pay as much attention to developing a sustainable crop rotation that provides stable, high methane yields as they do to producing the ideal mix of feedstock for their AD plants.

That’s the view of biogas crop specialists KWS UK which has launched a new guide to biogas cropping for the UK.

According to the company’s John Burgess, biogas producers should examine all the crop options long before they commit to commissioning an AD plant.

“While there are pros and cons for every biogas crop, early pioneers in the UK – backed by our experiences on the continent – suggest that basing gas production on one main feedstock crop could restrict your potential,” he says.

“While maize is often the lead crop in any feedstock mix as it is easy to manage, store and feed, producing a high methane yield/ha, it has a relatively slow retention time in the plant.

“Energy beet in contrast offers the highest possible yield/ha and the fastest possible retention time, so if it can be stored effectively is an ideal partner crop, and wholecrop cereals, while lower yielding per unit area can produce similar high yields/t.”

Mr Burgess says that KWS’ experience is that per tonne of fresh weight produced, the most effective feedstock mixes for maximum methane yield should comprise maize and wholecrop cereals.

However, when you look at the methane yield per hectare, utilisation of 10-30% energy beet alongside these two crops has a positive effect on output from the land area.

So it is a case of weighing up your land options, what crops suit where you farm and how these will interact with other crops on the same farm unit, before deciding on the right balance for your individual circumstance.

He points out that while care does need to be taken to ensure that the viscosity of the mix enables good functionality of the plant, the fast conversion rate of energy beet can help to buffer the gas production, raising the pH inside the plant, encouraging bacterial conversion of the complete feedstock to methane.

Energy beet also produces a cleaner source of methane than other feedstocks which enables more efficient conversion from methane to electricity through the combined heat and power (CHP) unit, or biomethane.

Mr Burgess admits that deriving the best mix for any one region is not easy. “We can draw upon the experiences of our colleagues in Europe to produce a best fit equation that should suit the UK regional rotation.”

As the only European plant breeder with a specialist plant breeding programme for biogas production, KWS is keen to share its expertise with UK growers, hence the production of what is its second guide to biogas cropping.

To find more info, please download our newly released ‘Biogas in Practice’ brochure (below) or copies of the guide are available from Elizabeth Hall on 01763 207300 – or email, elizabeth.hall@kws-uk.com.

Alternatively, growers seeking specific advice on which feedstock mix will produce highest methane yields/ha for their plans should contact John Burgess direct on 01763 207309.

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