A full version of this article appears in the magazine.

Agriculture is entering a period of change. New crops such as Miscanthus and Short Rotation Willow Coppice (SRC) are set to change cropping patterns and open up a new energy market to growers and the wider rural community.

Changes in the energy market have ensured that renewables have moved to centre stage, with climate change as the key driver. Biomass crops are widely regarded as being almost ‘carbon neutral’ because the carbon dioxide released when these crops are burnt as a fuel for heat and/or electricity is matched by the amount of carbon dioxide the plants absorbed when they were growing. As a fuel, they are therefore substantially more environmentally friendly than fossil fuels.

Miscanthus is a fast growing, clump-forming, non-invasive grass with a potential productive life of 20 or so years. Willow (Salix.spp.) is a diverse species, with several hundred varieties readily available within Wales. Its production is more comparable to agricultural cropping methods than it is to forestry.

Both crops are planted in the spring. Weed control is essential during the establishment phases and herbicides are routinely used. Mulches or cover crops can be used to help control weeds, with the added benefits of soil improvement. Trials on willow in upland areas suggest fertiliser applications may be beneficial and the addition of lime is likely to be essential in these areas.

There are no yield-damaging pests and diseases in Miscanthus crops currently, but SRC is susceptible to a number of insect pests, most particularly willow beetles, and also to diseases such as rust. The need to use insecticides can be minimised by careful plantation design and varietal selection. Resistant varieties are now being bred in an effort to reduce dependence on fungicides and insecticides.

Both crops have a good root system and well-developed mechanisms for recycling mineral nutrients, the roots helping to bind the soil together and reduce the risk of erosion. Miscanthus has a very efficient conversion of radiation to biomass, and a higher dry matter yield potential than crops such as wheat or barley. Both crops use a large amount of water, which is something that needs to be considered. SRC will grow well on most land where there is a reasonable level of rainfall, and is therefore well suited to the Welsh climate.

 

Site considerations

Miscanthus and SRC are fast growing, tall crops that can radically change the appearance of a site. With 85% of Welsh agricultural land under grass this is likely to be particularly an issue in Wales. Ploughing up long-term grassland releases large amounts of carbon to the atmosphere and this adversely affects the greenhouse gas abatement objective of biomass production. Energy grass crops can be grown on set-aside land and can make farmers useful additional income in the process, though from an environmental perspective this may not be desirable: much would depend on how species-rich the set-aside is, and how long it has been set-aside.

In order to be both economically and environmentally viable, crops need to be grown close to where they will be used as a fuel. The harvested crop is a bulky commodity, and the further it is transported the higher the carbon and financial costs.

 

Impacts on biodiversity

Ensuring that biodiversity isn’t negatively affected involves an understanding of the ecology of the current site and its surrounding area. Energy crops can create new opportunities for colonisation by many species of plants and animals, and a number of studies have been carried out in this area. SRC has been found to hold a higher density of birds and more species than cereal crops. The age of the crop is also important. Most species preferred a young crop, whilst tit numbers increased as the SRC crops became more established. Young crops of Miscanthus offer patches of bare ground that are popular with birds such as skylarks and lapwings, and the crop offers a good over-wintering habitat. Both SRC and Miscanthus are harvested in winter, which is outside breeding times and summer migrants are not present.

If properly planned, SRC and Miscanthus plantations have the potential to enhance the landscape and environment, reduce our dependence on fossil fuels and bring new markets to the rural economy. Farmers are the custodians of the environment and keeping them in business is key to keeping our rural heritage alive.

 

Catherine Heywood is Renewable Energy Consultant for ADAS and CALU.