Knowledge for better food systems

Biogas from grasses

November 2010
 An interview with Dr Nicholas E. Korres, University College Cork. Nicholas E. Korres is researching the production of methane gas from grass silage and how this relates to farm diversification. Having studied in Greece and in the UK, Nicholas is now a Research Fellow at the Environmental Research Institute, University College Cork, Ireland.

What is biomethane?

Organic material, such as grass, can be digested without oxygen to produce a gas or ‘biogas’. This biogas includes 55% methane and 45% carbon dioxide. To qualify as biomethane gas, it must be upgraded to the same standard as natural gas and have a methane content of about 97%.

What are the aims of your research?

My work is focussed on the digestion of grass silage to produce biomethane as a transport fuel. Its main emphasis is on examining the energy inputs required for this process and the greenhouse gas (GHG) emissions that arise. Additionally, I am undertaking a detailed analysis of the nitrogen cycle within the system of biomethane production. I hope this research will help to inform our understanding of biomethane:
  1. whether grass silage biomethane production can produce a renewable transport fuel,
  2. the role of grass biomethane in the diversification of agriculture under current EU agricultural and energy legislation, e.g. EC/1782/2003 and EC/28/2009.

Where are the greatest emissions in the biomethane cycle?

The GHG emissions from the full life cycle of biomethane production arise in two distinct phases of the production process. These are a. the production of the grass, and b. the biomethane production process. a) The production of the silage results in greenhouse gas emissions in the following ways: (i) energy used during the production of nitrogen chemical fertilizer produces  CO2 and N2O emissions expressed as kg CO2 equivalents ha-1,
(ii) the application of chemical fertiliser releases N2O, and
(iii) the application of lime releases CO2. b) The biomethane production process has both direct and indirect emissions:

(i) indirect CO2 from electricity use,
(ii) direct CO2 emissions from the heating of the digesters, and
(iii) losses of other gases during the process, for example, CH4. Emissions of N2O and CH4, are of particular concern due to their high global warming potential. Appropriate mitigation management of these two gases could contribute significantly in reducing the impacts of biomethane production on the climate. This can be achieved by the incorporation of the digestate, a residue of anaerobic digestion, back to the field as a substitute for chemical fertiliser or by incorporating animal manure into the silage digestate, to increase biomethane production efficiency.

What does your work on nitrogen include?

This research is assessing the GHG emissions from the production of biomethane using a mixture of grass silage and animal manure as the feedstock. This includes considering the management of the animal manure, the use of fertilisers and the emissions from the animals themselves. These include the release of methane gas from the animals’ ruminant fermentation process as well as nitrogen emissions from their excretions.

Single phase wet anaerobic digester
(continuously stirred tank reactor)

What are the main outputs from your work?

We will complete a series of publications on our research.  A final report based on the results of our research will also be published by the Irish Environmental Protection Agency. We have developed various “generic” LCA working protocols and methods, such as for the assessment of direct energy consumption and related emissions for the production of the feedstock (i.e. grass silage), and direct emissions expressed as kg CO2 ha-1 from the application of herbicides. To draw together research from this field, we hosted a conference here at the University of Cork earlier this year.

What were the main highlights from the conference you held?

The need for diversification in the agricultural sector and sustainable of energy within the European Union (EU) have advanced the role of grassland as a renewable source of energy in grass biomethane production yielding various environmental and socio-economic benefits. However, many factors continue to foster further intensification in the use of grassland, which generates significant environmental impacts. Research from our group proved that biomethane can meet the EU sustainable fuel criteria. These require a 60% greenhouse gas emission savings by 2020, compared to the emissions related to the use of conventional fuel (diesel in the case of biomethane). Biomethane can deliver up to a 75% reduction in emissions under various scenarios. Given the mature and well known technology in the agronomy and anaerobic digestion sectors, in addition to the need for rural development and sustainable energy production, grass biomethane is a potential solution that could fulfil many legislative, economic and environmental requirements. Further information and presentations from the conference can be found here.

How did you become interested in biomethane?

Two phase anaerobic digester

As an agronomist, I completed my PhD in plant science and population dynamics and was very concerned about the environmental impacts of energy and agro-chemical intensive crops. As a research fellow at the Agricultural University of Athens, Greece, I compiled a manual on 21 crops which have the potential to be used as energy crops. This included: seedbed preparation, crop establishment, husbandry (i.e. crop protection, harvesting, post-harvest management), energy balance and related greenhouse gas (GHG) emissions for each of these crops. It was at this time that I realised the importance of thorough planning and strategic decision making to achieve sustainability in energy crops, in terms of energy and related emissions. The opportunity to extend my knowledge came from my current position in the Biofuels Research Group at Environmental Research Institute, University College Cork, Ireland.
“Research from our group proved that biomethane can
meet the EU sustainable fuel criteria.”

Where would you like to take this work next?

Amongst other things, I would like to examine, in more depth, the environmental impact of various agrochemical substances used in energy crops. Additionally, I would like to integrate various scenarios of land use and land use change into LCA. Also, I would like to carry out more research into the methanogenic bacteria dynamics and anaerobic digestion. Finally, the role of multifunctional agriculture where the management of nature holds a key role for a sustainable production system is of special interest in my future research.

What do you see as the big questions for the food climate research community at the moment?

In terms of my work area, some important issues are:
  1. lack of a coherent publicly accessible database of information about inputs for feedstock production and processes in biofuel production chains,
  2. lack of a coherent methodology in LCA (e.g. allocation issues in LCA),
  3. site specificity of published results,
  4. application of LCA concerning various sectors of agricultural production,
  5. gaps in the classification and characterization of environmental impacts (e.g. various widely used agro-chemical substances impose different threats in human health regarding acute and long term effects). For example, the impacts of the use of organophosphate, carbamate, organochlorine and other pesticides (e.g. mild, moderate and severe poisoning along with cancer, neurologic, neuropsychological and reproductive system diseases).
  6. incorporation of LCA into land use change under various crop management scenarios, and
  7. examination of various scenarios for the inclusion of carbon sequestration dynamics in LCA.

Contact details

Dr Nicholas E. Korres, Environmental Research Institute
University College Cork, Lee Road, Cork, Ireland

Where can people read more?

Murphy J. D. & Power N. M. 2008. An argument for using biomethane generated from grass as a biofuel in Ireland. Biomass and bioenergy 33:3, 504-512;
Smyth B., Murphy J., O’Brien C. 2009. What is the energy balance of grass biomethane in Ireland and other temperate northern European climates? Renewable and Sustainable Energy Reviews 13:9, 2349–60;
Korres N. E., Singh A., Nizami A. S. & Murphy J. D. 2010. Is grass biomethane a sustainable transport biofuel? Biofuels, Bioproducts and Biorefining 4:3, 310–325.

Related Publications

Korres N. E., Thamsiriroj T., Smyth B .M., Nizami A. S., Singh A. & Murphy J. D. (2010). Grass biomethane for agriculture and energy. Sustainable Agriculture Reviews, Vol. 7 (in press).
Korres N. E., Singh A., Nizami A. S. & Murphy J. D. (2010). Is grass biomethane a sustainable transport biofuel? Biofuels, Bioproducts and Biorefining 4:3, 310–325.
Smyth B., O’ Gallachoir B. P., Korres N. E. and Murphy J. D. (2010). Can we meet targets for biofuels and renewable energy in transport given the constraints imposed by policy in agriculture and energy? Journal of Cleaner Production 18, 1671-1685.
Nizami A. S., Korres N. E. & Murphy J. D. (2009). Review of the integrated process for the production of grass biomethane. Environmental Science and Technology 43, 8496-8508. Photo credit : Photos of anaerobic digesters (credited to Dr. J. D. Murphy; Principal Investigator of Biofuels Research Group, Environmental Research Institute, University College Cork, Cork, Ireland).