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Comparative environmental life cycle assessment of cattle production systems - SCF0222

The main project aims to compare aspects of the environmental performance of different cattle production systems, ranging from conventional part housed and large-scale, fully housed dairy and beef to all-forage based production and including sub-set of organic production. The core method of analysis will apply systems-based environmental Life Cycle Assessment (LCA), using an enhanced version of the Defra-funded Cranfield model.

The main environmental impacts will include greenhouse gas (GHG) emissions, water quality (e.g. eutrophication potential) and air quality (e.g. acidification potential, NOx), non-renewable resource consumption, stress weighted blue water consumption and land use. Other areas, such as biodiversity, other non-provisioning ecosystem services and social aspects are out of scope, but are being addressed in a separate RC-funded, CEH-led project (Sustainable economic and ecological grazing systems – learning from innovative practitioners, SEEGLSIP).

The Cranfield LCA model will be enhanced to (a) incorporate the revised approaches now used in the UK’s GHG and ammonia inventories and (b) to support analyses of forage-based systems, especially those that conform to the Pasture for Life standards. The latter aspect incorporates two approaches. First will be the collection and analysis of activity data from Pasture for Life farmers by CEH to enable actual stocking levels to be quantified as grazing livestock units (i.e. 48,000 MJ metabolisable energy per year) per hectare. The existing site class based production model will be enhanced using both these data and applying a recently developed and tested grass production simulation model. Another aspect will be to identify the areas of grassland that are prone to soil damage by poaching (these would constrain extended grazing seasons). Comparisons of beef and milk production will be made using functional units to be agreed with Defra, e.g. per unit energy corrected milk, or per unit liveweight ready for slaughter or per unit weight beef carcass. A large scale sensitivity analysis will be conducted to address important variables such as: forage yields, grazing season length, milk yield, fecundity and soil carbon balance.

An assessment will also be made of the scale and seasonality of production that would be possible with forage-only based production, but based on the same land area as is used now for dairy and beef production. This will be a first order analysis, given that arable land currently produces crops like milling wheat for both flour for humans and wheatfeed for stock or malting barley that supplies a fermentable substrate and an animal feed.
Some animal feeds from overseas, such as soy meal, are implicated in major GHG emissions from land use change (LUC). Alternative approaches to calculating these will be scrutinised to recommend what is most appropriate for different types of analysis. The most suitable will be applied in this study.

The potential for home grown legumes to replace imported soya will be explored.
The overall aim is to compare the environmental performance of a wide range of cattle production systems using environmental Life Cycle Assessment (LCA). Limits on the outputs of such systems will be calculated and compared with current (and expected future) production levels.

Specific objectives follow.

1. Agree the core analyses that will be undertaken, the impact categories and the functional units to be applied
2. Upgrade the current Cranfield systems LCA model to be closely compatible with the revised methods for calculating GHG and ammonia emissions in the UK inventories.
3. Upgrade the grass models that support the LCA model to allow for seasonal variations in forage supplies and limits to access by grazing cattle to protect soils.
4. Obtain activity data from farmers using forage only based production to support model validation.
5. Characterise the impacts of overseas animal feed production, including soya, required for UK production
6. Undertake the comparative LCAs of forage-only based production with conventional and organic production, including sensitivity analyses.
7. Estimate the limits to production using a range of forage-only production systems compared with current production.
8. Estimate the potential for and limits to replacing soya in livestock diets.
Time-Scale and Cost
From: 2020

To: 2021

Cost: £112,847
Contractor / Funded Organisations
Cranfield University