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No. 349: Use of biomass in biogas plants - with a focus on energy crops

Mikkelsen, M.H. & Albrektsen, R. 2019. Anvendelse af biomasse i biogasanlæg – med fokus på energiafgrøder. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 43 s. - Videnskabelig rapport nr. 349. http://dce2.au.dk/pub/SR349.pdf

Summary

Since 2014/2015, the biogas plants have reported information regarding the biomass used in the biogas plants, and thus a four years data set is available. Based on the data reported, a database is provided, which has been used for a detailed analysis of energy crops used in the biogas production.

The use of energy crops only takes place on animal manure based biogas plants. The use of energy crops accounts for 59,900 tonnes in the crop season 2014/2015 increasing to 339,600 tonnes in 2017/2018, corresponding to a four-fold increase. The use of energy crops is more common for farm level biogas plants and accounts for 8-10 % of the total biomass input, compared to common biogas plants, where the crop energy accounts for 1-5 % of the total biomass input. Maize is the most common used energy crop type and for 2017/2018 maize constitutes approximately 88 % of the total amount of energy crops at the common biogas plants and approximately 60 % for the farm level plants. There are large variations in the use of energy crops across the biogas plants and in total 61 biogas plants have used energy crops in one or more year, of which 19 plants used energy crops in all four periods. Regarding the use of energy crops, it may be relevant to pay attention to the use of the biomass category “discarded crops”. During the four reported years, 42 biogas plants used discarded crops, of which 37 plants also used energy crops. Thus, a clear definition of when a crop should be defined as "energy crops" or as a "discarded crops" is needed.

For crop season 2017/2018, 17 animal manure based biogas plants uses energy crops at a level, which account for more than 10 % of the total biomass, and for a single biogas plant the energy crops is more than 20 % of the total biomass input.

It will be relevant to investigate the possibility that all required information regarding biogas plants, or as many as possible, is reported on site and preferably in a digital form.