Miscanthus and its many co-benefits

Anita Shepherd, University of Aberdeen

Artwork: Dr Cécile Girardin

At the University of Aberdeen, Astley Hastings and myself have published several papers on projections for bioenergy crop Miscanthus x giganteus. I have travelled across England looking at commercial crops from Worcester to Norfolk and what I have discovered is that our commercial miscanthus are robust bioenergy crops against weather events, they sequester soil carbon on low grade agricultural land, and have a ready market of small power stations to use them.

The key why miscanthus is so sustainable lies in its ability at end of season to reabsorb its nutrients into the rhizome for efficient re-use next season. This in turn means a mature crop does not require fertilizer and, with a good crop cover, requires little herbicide, low field management is popular with growers and encourages wildlife, low field spraying is popular with urban communities.

Miscanthus is perennial and projections for bioenergy policy have traditionally assumed a mature crop. Mature English crop yields are commonly 12 t ha−1 year−1, second‐third‐year juvenile harvests average 7 t ha−1 year−1. From surveying crop age and yield from commercial growers, this means that a surrounding 10 km by 10 km area of distributed crop age averages 9 t ha−1 year−1. A landscape with recent miscanthus uptake means many juvenile crops have not attained full yield, and on average we can expect a region to contain stands of a mix of ages which brings down the mean yield when policymakers need a spatial composite value. It is important not to over-estimate yield to give growers and future investors a realistic expectation.

So far miscanthus has been produced by rhizome propagation, a slow process meaning wait times for growers wishing to plant a new crop. Small rural bioenergy power stations rarely have sufficient miscanthus bales to burn so augment using less thermally efficient wheat straw bales. To combat this, the University of Aberystwyth and bioenergy company Terravesta are part of a consortium developing seed-propagated rhizomes to upscale production of miscanthus, and my fellowship works with them to look at the production capability of the new miscanthus hybrid.

From surveying growers, their main reason for investment in miscanthus is not financial return, but relates to its ability to solve problems with its low maintenance cost and regeneration, and also offers extra income as gamebird cover. It offers a solution for fields with difficult vehicular access, and remote second farms. Miscanthus attracts spiders, beetles and birds, wildlife is abundant in these fields, largely undisturbed except for harvest which contributes to the greening of agriculture. What I have discovered is that growers are pragmatic people and miscanthus is a useful crop, it is increasingly seen as a practical solution to farming and social, as well as renewable energy issues.

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