2015-04-01   facebook twitter rss

A La Carte Menu for Anaerobic Digesters

A range of crops can be considered as feed stocks for anaerobic digesters and growers don’t need to stick to one or two, according to Limagrain’s Martin Titley.

“A number of crops can be used on a rotation and, through careful cropping, output from the available hectares can be maximised,” Martin Titley says.
“Recent reports are suggesting that feed stocks from waste – either food or crop - are at capacity so the focus, as the number of plants increase, will be on crops. Of the current 157 AD plants in the UK, 80 are crop fed which requires approximately 20,000 hectares of land.”

Blizzard - a ‘clean’ fodder beet

Blizzard - a ‘clean’ fodder beet

With planning granted for a further 415 anaerobic digester plants, a significant increase in demand for feed stocks from crops looks likely,” he adds.
“Based on these figures we would be looking at a further 35,000 to 40,000ha worth of crops to feed these AD. Even if some of the plants are not developed, the increase on demand for feed stocks from crops will be significant.”

Feed stocks for AD plants are not confined to a limited number of crops. “There is quite a range that might be considered,” adds Mr Titley. “It really depends on land type, equipment labour availability and the farm system. Also, some careful planning of the rotation can increase annual output significantly.”

Maize is often the favoured crop in the south and east. A 500kw digester requires approximately 220ha of maize silage yielding around 50tonnes of fresh matter. It has an excellent biogas yield and it can be grown continuously, but Mr Titley suggests that growers could often improve productivity by selecting the variety that best suits their system.

“Don’t assume late maturing varieties are best. The land might be better suited to an early maturing variety which opens up the options of an extra feed stock off the land.”

Harvesting the maize earlier can mean that a grass can be sown in September or early October and that can be harvested the following spring. Alternatively, a winter rye crop also for feed stock can be sown after the maize harvest which is then harvested as wholecrop in late June or July and can be then followed again by grass. “It’s worth looking at these options for the individual farm.”

Fodder beet is becoming an increasingly attractive option to supplement maize and of course where maize can’t be grown due to its huge energy yields, high sugars and fast fermentation. “It’s a robust crop,” adds Mr Titley. “It is suited to the UK’s temperate conditions and it’s a low risk crop - yields are reliable,” he adds, although he encourages growers to select a very clean variety.

Blizzard is a good choice – UK trials have shown that it has a very low dirt tare compared to some other energy beets and this means that it may not need to be washed as much before use. This is a great advantage.”

With sowing options in spring or autumn, specifically developed grass seed mixtures that give good yields, are fast growing and offer consistent quality are good choices for AD plants. Power Grass, a mix of Italian ryegrass and westerwolds, is a prime example. Its sowing and harvesting flexibility means that it can be grown on an 18 to 24 month rotation and best overseeded annually to maintain yield and longevity.

“Grass can greatly help increase the annual productivity of the land used for feed stock,” adds Mr Titley.
“Wholecrop cereals offer similar advantages as part of a rotation or in areas with less fertile soil that may not be suited to maize.”

Mr Titley encourages growers to look at all the options of feed stocks. “Weigh up the pros and cons and look carefully at matching the crop and the variety or mixture to the area, soil type, farm system and resources available.”


  Related Links
link Fodder Beet Trial Data Show Benefits of Top Varieties
link Glyphosate is Not a Human Health Risk
link Coexistence of GM and Non-GM Products is Possible
link CPA Sets Out Policy Priorities for the Next Government

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