Maize quality key to higher methane yields
With forage maize emerging as the favoured feedstock for producing biogas energy on-farm, a leading maize breeder is advising farmers that variety choice could prove significant to final energy yields.
The natural tendency might be to select maize varieties with the highest dry matter (DM) yield. However, recent work in Europe by Syngenta Seeds indicates a strong correlation in maize between energy content and methane yield.
Nigel Padbury, maize technical, sales and marketing manager for Syngenta Seeds, advises growers to check the variety’s quality data as simply choosing the variety with the highest DM yield may not be the best solution. If metabolisable energy yields are poor, methane yields are likely to be low.
He also notes that where an anaerobic digestion (AD) plant is found alongside a livestock enterprise, growers should choose varieties that are multi-purpose; suitable for AD and feeding cattle and so providing easier on-farm management and control of costs.
NK Bull has the highest ME yield on the 2010 NIAB Forage Maize Descriptive List, making it an obvious choice as a maize variety suitable for anaerobic digestion. NK Jasmic also fits with its exceptional combination of high yield and quality.
"Choose varieties that can reach 28-32% dry matter in a normal year; anything higher and the gas output drops. Forage maize varieties NK Bull and NK Jasmic could be ideal for biogas production with exceptional metabolisable energy (ME) yields of 225,000 and 223,000 MJ/ha respectively.
"A biogas plant has similar feeding needs to a high performance cow so variety choice and quality of the feedstock should be similar. The digester should be compared to a cow’s rumen where the bacteria need a stable, consistent feedstock; some low grade basic feed to act on and a high energy feed to stimulate the digestive process. In the UK it’s likely that on-farm digesters will use a combination of slurry, as the low grade basic feed, and forage maize providing the high energy substrate," says Mr Padbury.
