by Mariecia Fraser
A few months ago, we were shocked and deeply saddened to lose our friend and colleague John Corton. This blog is about an area of research he was tremendously passionate about.
Managing native grassland is a challenge right across Europe. Its low nutritional value together with declining stock numbers has increasing led to under-grazing and agricultural abandonment. But what other land use options are there for unimproved, semi-natural vegetation? Especially if it’s been taken over by problem plants such as bracken, rushes and Molinia (purple moorgrass). Dominance by these brings big biodiversity challenges, and large areas of hill land are now being mown by conservation bodies such as the RSPB, National Trust and Natural Resources Wales to try and maintain habitat value.
ProGrass was an EU project which was the first to consider bales of discarded vegetation being produced by this type of land management as a potential feedstock for bio-energy. IBERS worked with partners in Germany and Estonia to test a pilot processing plant that turned this biomass into a liquid substrate for anaerobic digestion and a dry cake for burning. The vegetation was cut and baled using standard (but robust!) farm machinery any time from mid-August on. One of the advantages of using this type of vegetation as a bio-energy feedstock rather than a forage is that the decline in herbage quality over the autumn and winter doesn’t matter. And waiting until the ground is frozen can mean areas that would normally be too wet to access can be cut, helping to knock back e.g. rushes. Lots of great data was collected as the processing plant (known as Blue Konrad to his friends) toured across Europe. Testing of the material produced confirmed that minerals that could damage boilers had been removed from the dry cake, making it suitable as a fuel.
Several follow-on projects have taken the ProGrass concept further. Burning material at high temperatures without oxygen (a process known as pyrolysis) produces char, which everyone who’s ever had a go at cooking with charcoal knows has a high heat potential. It’s also a great way of concentrating energy into something small and light. Mobile char rigs could offer a great way to make the most of material located in inaccessible areas that would be too costly and difficult to transport out as bales. The latest project has us working once again with several of the ProGrass partners plus new collaborators across Europe to broaden the range of ‘waste’ green material being considered even further.
If the technical challenges of scaling up can be met and the economics work out we could have a triple win: reduced reliance on fossil fuels without growing extra biomass crops; improved biodiversity; and an alternative income stream for land managers. And there’s an awful lot of land we can use without damaging sensitive areas. The ideal set up could be to establish areas that are cut annually on a rotational system; with stock grazing on the greener, more nutritious, growth the following year; then a fallow year or two to build up the biomass again. At a landscape scale this would be a great way of creating mosaics of vegetation at different ages and heights – just the sort of thing our rare upland birds and other wildlife love.