Straw as energy source underestimated
Straw from agriculture could supply energy to many millions of households, researchers at the TLL (Thueringian regional institute for agriculture), the DBFZ (German biomass research center) and the Helmholtz Center for Environmental Research (UFZ) reported in the journal Applied Energy.
The authors say that straw has been under-utilized as a biomass residue and waste material.
Prof. Daniela Thrän and colleagues found that from the 30 million tons of cereal straw produced each year in Germany, between 8 and 13 million tons could be sustainably used for energy or fuel production.
Straw could heat millions of homes
Just that straw from cereal production could provide from 1.7 million to 2.8 million average households with electricity, and simultaneously 2.8 to 4.5 million homes with heating.
The authors wrote “These results highlight the potential contribution of straw to renewable sources of energy.”
In this study, the scientists gathered and analyzed data on the development of residual substances resulting from agriculture in Germany. Straw, which accounts for 58%, is the most important resource. However, its use for energy production has been less than negligible.
During the second half of the last century there was a steep rise in the cultivation of winter barley and wheat, as well as rye in Germany, this production has remained constant since the new millennium.
In order to remove compounding factors, such as weather fluctuations, the team took average values from 1999, 2003 and 2007. During those three years, approximately 30 megatons of cereal straw were produced each year (average).
Only half of the 30 megatons can be used as an energy resource. Parts of the straw cannot be used, and a certain amount is utilized as bedding in livestock farming.
Some of the straw must be scattered over the agricultural land to prevent nutrients from leaving the soil.
One third of the straw could be used for energy production
The scientists calculated that in Germany, from 8 to 13 megatons of straw could be used sustainably each year for the production of energy, without undermining the quality of soil.
Prof. Thrän said “To our knowledge this is the first time that a study like this has been conducted for an EU country, demonstrating the potential of straw for a truly sustainable energy use, while taking into account the humus balance.”
The researchers believe straw can contribute to the future energy mix. How much it might contribute to greenhouse gas reduction depends on how it is utilized. They calculated that emissions compared to fossil fuels may be from 73% to 92% less when straw is used to generate heat, or heat combined with power generation.
Dr. Armin Vetter, who works at TLL, said “Straw should therefore primarily be used in larger district heating stations and/or combined heat and power stations, but technology must be developed for an environmentally-friendly utilization.”
Dr. Vetter has been operating a straw-fuelled power station for 17 years.
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