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Sessions & Workshops
Greenhouse gas emissions from grassland systems
Grassland farms are sometimes criticised for their levels of greenhouse gas emissions. How real is the problem and how easy is it to take action? (Organised by SRUC)
Christine Watson (Scottish Rural College): Chair
This session explored the complex issues surrounding ruminant livestock’s contribution to climate change. Results from recent studies were presented and an overview given of some of the practical, on-farm mitigation measures that can be introduced. The session highlighted that although it may be difficult to do anything about ‘belching cows’, more efficient management can help to reduce impact in this area and improve profitability.
Dave Roberts gave an overview of the SRUC Dairy Research Centre’s work on greenhouse gas emissions from livestock, highlighting that in their trials, dairy cows fed with higher amounts of concentrate were found the have lower methane emissions. Their work also illustrated the importance of good quality forage for reducing methane from dairy cows and the effects of trampling and tractor compaction on nitrous oxide.
Ross Paton then presented on the actions they had taken on Torr farm, pointing out the value of record keeping for environmental impact assessment and cost saving. Ross highlighted that the main message from carbon footprinting is to be more efficient with farming practices, e.g. through making better use of manure and boosting livestock productivity. Ross also mentioned that it is better to explore on-farm efficiency options first before investing in renewables.
John Kay, Wastes Advisor from the National Trust then presented an overview of the ‘What’s your Beef’ report published by the National Trust in 2012. This report compared greenhouse gas emissions from 10 farms across the UK. Although the 4 organic systems within the study performed slightly worse in greenhouse gas terms than conventional, when carbon sequestration from grassland was included within the assessment, the organic footprint was lowered considerably.
The discussion highlighted that not all carbon is the same; whereas non-organic carbon drives the conventional sector, organic farmers rely on the natural carbon cycle. Similarly, coal and other fossil fuels have been built up over millennia and emissions from these sources should not therefore be compared on the same basis as emissions from cattle and sheep. The importance of expressing greenhouse gases per unit of land was also highlighted, as for farmers in the UK this is the most limiting factor.
We need to retrieve more information on carbon sequestration, based on field and laboratory analysis, so that a reliable assessment can be made of this area. Some members of the audience expressed frustration that this aspect is excluded from many assessments as it means that the full benefits of organic systems are not being realised.
It was also highlighted that the ‘saturation effects’ of increasing organic matter content should not stop us from encouraging sequestration through grassland/livestock systems, as the effect overall is still significant. The importance of dual purpose breeds of dairy cattle was also mentioned in the discussion, as they can increase efficiency in terms of CO2 considerably through splitting the global warming impact across two product types. A comment was also made that it is a mistake to equate carbon from fossil fuel reserves with carbon that is cycled in agricultural systems, as fossil fuels have been built up over millennia.
Discussion points:The discussion that followed the presentations brought out the following points:
- A functional unit of per acre is the most appropriate when comparing systems as this is the limiting factor in the UK
- It would be helpful to compare the outputs of systems on a common basis (e.g. unit of energy and/or protein produced) rather than focusing on one product type such as litre of milk
- The benefits that animals provide within mixed farming systems should be recognised and captured within assessments.
- Need to highlight the true environmental costs of conventional systems in the agricultural press; considerable ignorance at the moment relating to the fossil fuel intensive nature of production systems (e.g. the amount of energy required to produce fertiliser for conventional arable systems, or the land use changes associated with imported feed)
Speaker presentations and abstracts
Dave will summarise some of the recent work at SRUC Dairy Research Centre, Crichton Royal Farm Dumfries. Two dairy farming systems were compared between 2003 and 2010 with cattle on high forage and a low forage system. The enteric methane production from the cows on these systems was estimated and cattle on the high forage system produced approximately 25% more methane /litre of milk than the cows on the low forage system. A desk top study was also undertaken which showed that improved silage quality resulted in lower enteric methane production per litre of milk. The effect of soil compaction by machinery and cattle in the autumn on spring grass yield and nitrous oxide emissions has been investigated in an experiment funded by DairyCo. The compaction treatments had an effect on N2O emissions with the mean tractor compacted plots showing the greater emissions compared to the trampled and control plots (24.5g ha-1 increase compared to the control over the growing season), especially after the first fertiliser application (14.9h ha-1 increase in emissions compared to the control). These experiments and the new dairy farming systems , including one with all feed grown on farm, will be discussed.
Ross Paton (Torr Farm): Practical on-farm measures (3.3MB)
I will speak about the experience I’ve had with the Scottish Government climate change focus farm project. The things which have stood out are not so much energy use but efficiency of resource use and land management especially within an organic context. Efficiency and organics are not contradictory as some would have us believe. The key is not to waste resources and that tight management can make a huge difference to greenhouse gas emissions on farms. Efficient feed use, good soil management, good use of on farm resources are key. Other examples include minimising handling of waste water, thoughtful use of water generally and avoiding pollution. All of these help mitigate greenhouse gas emissions in indirect ways.
Rob Macklin (National Trust): Comparing the carbon footprint of different beef systems
In summer 2012, The National Trust published its “What’s your beef?” report as a contribution to the debate on the carbon impact of livestock production. The report was designed to sense-check the carbon accounting that appeared to discredit extensive systems as inefficient – according to calculated kg liveweight gain /kg CO2e. As the vast majority of Trust farms are based on extensive livestock production on land unsuitable for arable cultivation, we sought to check how a selection of our beef farms might compare. Independent consultants compiled the carbon scores from farm visits using standard PAS 2050 methodologies and a desktop comparison of overseas systems, including Brazilian Cerrado and US feedlot. Results from our farms were in line with published results elsewhere. However, when standard carbon sequestration figures were included in the analysis, the carbon balance shifted to favour extensive systems despite their having lower emissions efficiency. Essentially, extensive beef systems have the potential to approach carbon neutrality despite taking longer to reach slaughter than more intensive cereal based systems. We recognise that rates of carbon accumulation and loss are uncertain and we are keen to see routine soil organic carbon testing to check the trends in real situations over time.