BESOS

"BioEnergy, Soil and Climate Change: factors and mechanisms on C storage and N2O emissions after bioenergy by-products application in soil"

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 Obiettivo del progetto (Objective)

'The interest in using renewable energy is continuously increasing. Biomass is the most common form of renewable energy and recently, much attention has been paid to identifying suitable biomass sources which can provide high energy outputs to replace conventional fossil fuels. An important, but little understood aspect surrounding biofuels (fuels obtained from biomass) is the overall impact on global C and N cycling. Probably the increase of energy production from biomass will lead to higher input of its by-products to the soil as amendments or fertilizers. However, it is still unclear how these novel by-products of bioenergy production will influence microbial transformation processes in soil, and thereby its greenhouse gas balance and organic matter reserves. Particular attention has to be paid to changes in the C balance of the soil and changes in N2O emission of the soil, as these may negate any benefits made by biofuel production in terms of Global Warming Potential. With this project, I aim at studying the impact of different bioenergy by-products on C and N biogeochemical cycles. The study will focus on residues from two bioenergy chains (anaerobic digestion and pyrolysis), but novel bioenergy by-products from new developing tecnologies (such as residues from third-generation biofuels from algae) will also be included at laboratory scale. C and N mineralization in soil will be followed using a combination of 15N and 13C labeling units. Dynamics of CO2 and N2O will be studied in the field and under controlled conditions (laboratory experiments). N2O emitted per unit stabilized C will be quantified. This novel ‘efficiency parameter’ for C sequestration will be related to the different properties of the biofuel by-products. The integrated results of these experiments will help to understand the impact of the different bioenergy chains on C an N cycles, which may have a high impact on life cycle analysis calculations for the different bioenergy chains.'

Introduzione (Teaser)

Biological material from living organisms, usually referred to as biomass, is the most common source of renewable energy. An EU-funded initiative investigated the effect of by-products from this source of bioenergy on the soil environment.

Descrizione progetto (Article)

Increased energy production from biomass could lead to higher levels of its by-products in soil. However, it is not yet clear how these by-products will affect microbial processes in soil, including the production of greenhouse gases.

Particular attention therefore needs to be given to changes in the carbon balance of soil and changes in nitrous oxide (N2O) emissions from soil.

The BESOS project was therefore established to investigate the impact of different by-products from bioenergy fuels on biogeochemical cycles.

The initiative focused on residues from two forms of bioenergy: anaerobic digestion and pyrolysis. Anaerobic digestion breaks down organic material using microorganisms in the absence of oxygen and produces biogas and a solid by-product called digestate.Pyrolysis implies the thermal decomposition of biomass at high temperatures and generates bio-oil, a mixture of gas and a solid by-product named charcoal.

Biochar is the name given to charcoal when it is added to soil. BESOS applied the material to 15 agricultural soils with different pHs and textures from different areas of Brazil, Spain and the United States. Researchers observed a consistent and significant decrease in N2O emissions following biochar application.

The mineralisation of carbon and nitrogen in soil was studied both in the field and under laboratory conditions using nitrogen-15 and carbon-13 labelling isotopes. Scientists also measured levels of N2O.

Results from these experiments were compared with the different properties of the bioenergy by-products. They showed that biochar helps in the last step in denitrification, whereby N2O is transformed to nitrogen gas. Biochar reduced N2O from soil on average by about 54 %

Results from the BESOS project will provide a better understanding of the impacts of bioenergy by-products on carbon and nitrogen cycles. This may have a significant impact on life-cycle analysis calculations for different forms of bioenergy. In addition, the data can inform future policy decisions related to biochar as a soil additive and its effect on greenhouse gas emissions in agriculture.