Can grass be greener

Published 21 November 14

Gone are the days of grass being used solely for production of meat, milk and wool – the latest hot topic is creating bioenergy and biofuels. Here, Dr Debbie McConnell explores the opportunities for dairy farmers.

Research presented at the 50th European Grassland Federation (EGF) conference, held in Aberystwyth in September, highlighted the important role biomass energy production is playing in strategies to meet energy demand and combat climate change impact all across Europe.

Research presented stated that due to declining ruminant numbers (122 million in 1975 vs 96 million in 2006), there will be an estimated surplus grassland area of 9-15 million hectares in the European Union by 2020, about one-fifth of the area of permanent grassland.

With a rapidly developing bioeconomy, there is scope to utilise this ‘surplus’ to meet rising demand for sustainably produced biomass for both renewable energy production and bio-based products.

Different bioenergy uses for grass

It’s commonly known that one of the most common bioenergy uses for grass and maize forages is in anaerobic digestion plants, where fermentation drives methane production. This is now so well established, recent statistics show that up to one-third of the area of maize planted in Germany is destined for biogas plants.

Beyond this, however, more complex processing and biorefinery of grass is producing a new range of products. This often involves pressing either grass or silage to extract the juice, with different components of this juice (for example, lactic acid, amino acids, sugars) then extracted for use in the production of plastics and nutrition supplements.

Ongoing work at Aberystwyth University is also investigating the potential for using grasses with high water-soluble carbohydrate content to convert fructose in the juice to ethanol for use in biofuels. The pressed cake remaining has applications in insulation materials, bio-composts, paper, peat substitutes and thermoplastics, and also as a solid fuel source for combustion.

greener grass

 

Suitability of grass for bioenergy production

Some grasslands are more suited than others to bioenergy production. High-yielding, intensively managed, improved grasslands supply rapidly degradable grasses which can produce high yields of methane in biogas production plants and are similarly suitable for biorefining processes.

In contrast, semi-natural grasslands and lower quality grasses tend to have higher levels of lignin and require treatment before the fermentation process can break down the cellulosic fibre for methane production. Likewise, these grasses tend to have too low a content of exploitable ingredients to justify the extra treatment needed to extract these compounds, and cost recovery is difficult without subsidy.

Nonetheless, research and innovation in biorefinery of grass is continuing to grow and the exploration of this area offers potential diversification options for farmers in the future. It also raises challenging questions over competition for land use and the current ecoservices semi-natural grasslands offer to meeting EU requirements.

 

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