The task of researching the use of a piece of agricultural land for biomass planting brought me down a strange alleyway. I wanted to assess the benefits of growing biomass for CO2 savings and for profit, but I wanted to compare this to the pros and cons of growing food on the same land.
Miscanthus (elephant grass)offers the best bang for buck for biomass, it has a short growing season and can be harvested in a short time. But in order to make the biomass useable it must be compressed into briquettes or pellets. so there is a considerable capital investment in plant and equipment. But a hectare can produce about 6.6 tonnes of useable biomass, which in turn can provide useable heat for four to five new-build properties. That’s a saving of about 5 tonnes of CO2/hectare.
Other biomass uses such as Short Rotation Coppicing can produce good yields on similar land, but there is a wait of three years for the crop to mature, then one third of the crop can be harvested per year from then on with little further investment. The fuel can be chipped or pelleted.
In both cases the best use of the fuel is to use it nearby so that there is minimal CO2 emissions for transport.
If the land is arable what is the best crop to grow from a C emissions standpoint. We import a lot of food into the UK, so displacing food that we import offers the best solution. We should aim to minimise our food imports by maximising our arable land use in the UK. There are lots of options for displacing food imports, but not all of them are straightforward. Some imports, such as bananas will not be ever easily grown here, until climate change really takes hold. But some are very straightforward, and I wonder why we have allowed ourselves to get into a situation where we import potatoes and carrots into the UK. By air. Every tonne of potatoes imported by air produces around 2 tonnes of CO2. A hectare of arable land can produce 45 tonnes of spuds a year, so that is a displacement of 90 tonnes of CO2 per hectare, rather better than the savings from biomass of 5 tonnes from the same land.
Carrots are even worse because we tend to import them from South Africa. Why we feel the need to do this amazes me, how can the economics of this work? However they work we need to find a policy mechanism to stop it from working and to reward UK and Irish producers for producing them instead. Air freighting in carrots costs a whopping 5.5 tonnes of CO2 per tonne,, but a hectare can grow 52 tonnes of carrots. So a single hectare can displace 286 tonnes of CO2 by growing carrots. This is 35 times better than growing biomass. Each carrot could be housed in its own individually heated bell jar and provided with piped recordings of Prince Charles and still come out better.
But does this make economic sense? Is biomass more or less valuable than carrots? Well thankfully yes, so 6.6 tonnes of biomass will yield approximately £1400 per hectare, but carrots retail at £470/tonne so will yield £24,440 per hectare.
The conclusion is straightforward, land should be used for growing food, both from an economic and a CO2 perspective, growing biomass only makes sense on land that cannot possibly be used for any other purpose.
The carbon footprints of foodstuffs are taken from here