Land Use & Agriculture


We have shown in the Zero-Carbon Britain series that a successful decarbonisation programme cannot be achieved without due attention to the food and land-use sector. This is because the sector is both a strong source of GHGs in its existing state and a potential sink if suitably redesigned.

We created several models of the UK food commodity system that appear superficially complex but are basically very simple and can easily be evaluated and subject to critique -- which of course is welcome.

There is a persistent difficulty in tracing the progress of food commodities through the food chain in a quantitative way. It is difficult to get the raw commodities to match up with the food as consumed. An approximation is given in the following 'Sankey Diagram':

This 'Sankey Diagram' (showing the same quantities transformed from left to right) attempts to quantify the flow of 'biomass' from its origins in UK and overseas land through to useful consumption within the UK. Units are simply 'tonnes of biomass as reported', but accuracy is limited by varying quantities of water included in the measurements. However, taking the diagram at face value several things are striking. There are systematic losses through the system, and most biomass does not lead to useful products in the human economy. The livestock sector, although of great cultural importance, is particularly inefficient in its use of resources relative to what it delivers. 

This 'Sankey Diagram' (showing the same quantities transformed from left to right) attempts to quantify the flow of 'biomass' from its origins in UK and overseas land through to useful consumption within the UK. Units are simply 'tonnes of biomass as reported', but accuracy is limited by varying quantities of water included in the measurements. However, taking the diagram at face value several things are striking. There are systematic losses through the system, and most biomass does not lead to useful products in the human economy. The livestock sector, although of great cultural importance, is particularly inefficient in its use of resources relative to what it delivers. 

The low-carbon land-use approach taken in Zero-Carbon Britain generates a number of scenario variants, but they all share a great reduction of grazing livestock, releasing grassland for alternative, non-food uses. Loss of food production is more than made up by release of arable land no longer required for livestock feed. To those for whom this approach is novel, the scenarios might come across as bizarre and shocking. But there appears to be no other approach consistent with meeting the requirements of 'fairness and physics'. Criticism is of course necessary and welcome, but so far no critic has succeeded in demonstrating a flaw in the reasoning or calculations.

Here the approach is summarised in three different formats.

Land Use in Zero-Carbon Britain 2010 (doc)

Low-Carbon Land Use (ppt)

Food and Land Use Modelling Spreadsheet 2013 (Excel)

The last item, a spreadsheet, lays out a basic model that can be examined in every detail, and gives references. It is fully active, and allows users to model scenarios of their own in column Z. 

One of the acknowledged uncertainties of the ZCB scenarios is the fate of sequestered photosynthetic carbon. One attractive possibility is to maximise the use of biomass in the physical fabric of the economy, particularly buildings. This has not been deeply studied, but some of the issues are explored in

Building Materials Derived from Biomass 2011 (doc)