While maize has set the pace as a feedstock for biogas plants, new trials confirm that energy beet could be even more effective in UK conditions.
According to KWS UK, energy crop specialist, Simon Witheford, not only does it provide the highest dry matter and methane yield of any crop it can also be handled and stored as easily and cost-effectively as maize.
In Independent energy beet trials on Lincs brash in 2012, the best variety produced a 3t/ha higher DM yield compared to Magnum, from roots that weighed in at 87t/ha.
Thats 20% more dry matter per ha with the potential to yield 500m3 more methane/ha, enough to generate the equivalent of 500 more electricity per cropped ha compared to lower dry matter types.
Based on these DM yields, the significant increase in methane provided is a major boost towards maximising energy output per cropped area and helps make energy beet a no brainer in the UK situation, says Mr Witheford.
Indeed, after a year when maize has suffered due to lack of sunlight and heat units, growers in the UK are increasingly finding that energy beet helps provide yield stability as a more robust and reliable source of feedstock, he says.
Mr Witheford points out that these trials are not a one off. In 2011 KWS specialist high dry matter energy beet varieties Gerty KWS and Lissy KWS also produced exceptional dry matter yields of 19-21t/ha from dry matter (DM) percentages of 27-28%.
Similarly, in the 2012 trials, Gerty KWS and Lissy KWS again gave 19.4 and 17.4t/ha of dry matter, proving their consistency at what was a more difficult site and season compared to the very dry 2011 summer/autumn.
Front runner for yield in 2012 was Debby KWS at 19.9t/ha DM and Mr Witheford suggests it is a step ahead of currently grown varieties, demonstrating some of the advances being made by the companys breeding team.
Mr Witheford points out that there are a growing numbers of UK biogas producers now looking at using beet at up to 30% inclusions rates in their biodigesters. While maize is often the lead crop in any feedstock mix, 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 of crops suited to the UK environment, so is an ideal partner crop to maize in the digester, he says.
In another step forward for 2013, we are also introducing the first energy beet with tolerance to beet cyst nematode, Becky KWS, which will be of benefit to those cropping beet for biogas in areas where sugar beet has been widely grown and the pest is found. At 18.6t/ha DM in the trial it is no slouch.
The two years of UK data shows that growers can easily produce energy beet dry matter yields on a par with those of specialist maize varieties, says Mr Witheford.
In practice, the only limitation to energy beet production is the ability to be able to get on the ground to plant and then harvest the crop, he suggests.
Geographically, energy beet can be grown across the UK, but production is more limited on those soils that are still at field capacity in mid-April and/or return to field capacity at around the end of October.
Unlike maize which needs to be harvested by a certain date, energy beet can be left in the ground and harvested when convenient. Maximum yields are achieved in mid-late November so growers should not harvest much before this time.
Mr Witheford says that close rotational cropping of energy beet should be avoided or growers could create soil borne pest and disease issues.
As with other silage crops soil tares are commonplace. However, the harvesting process and the use of a cleaner loader will remove most soil and new energy beet cleaning systems will be introduced to the UK next year.
Most UK growers use clamping methods similar to those adopted for maize, but the beet needs to be stored whole and not chopped as for maize. The beet settles quickly in the clamp and does not require any rolling or compression as this will damage the root and make it susceptible to infection and degradation.
Within 1014 days of ensiling, the beet goes through three of the four steps required in anaerobic digestion, stopping short of the production of methane through methanogenesis. Thus the ensiled beet works faster and produces methane more quickly than freshly harvested beet.
The fast conversion rate of the beet helps to buffer gas production, raising the pH of the biodigestate mix, encouraging bacterial conversion of the complete feedstock to methane.
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.
Our experience is that beet is wholly complementary to maize or wholecrop cereals within the AD plant and with maize production unrealistic in some regions of the UK, it is proving a highly acceptable alternative, says Mr Witheford.