ISCF WAVE 1 AGRI TECH: Formulating novel fertilisers and land conditioners from bioenergy wastes

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In the face of finite sources of conventional phosphorus, and highly energy-intensive and price-sensitive nitrogen, agriculture is challenged to maintain or increase food production and simultaneously reduce its carbon impact. Fertiliser prices are strongly influenced by the crude oil price, reflecting the energy intensity of the manufacturing process. Finite nutrient sources are being depleted, whilst nutrients are lost from the land through crop harvest. It is therefore necessary to identify alternative sources of nutrients which can be safely applied to crops to sustain food production which can be produced with lower carbon impacts, and less environmental damage. The proliferation of the renewable energy sector, as a means of reducing carbon emissions, has resulted in the growth of biomass to energy schemes. Agricultural land is the "expected" sink for digestate in the UK according to government policy since these waste sources are nutrient-rich. However, a number of limitations restrict the use digestate: highly variable composition (both spatially and temporally); undesirable compounds and contaminants presence (excessive metals; plastics residues); lower nutrient content than in manufactured fertilisers (higher volumes applied); logistical constraints (spatial dispersion from source); temporal constraints (application limited to certain periods, thus need for interim storage); uncertainties of crop responses. These undesirable factors have resulted in it being a disposal cost to the AD operator (average £3.73/t in 2013). Ash is similarly plagued by inconsistent composition and other undesirable characteristics and so significant quantities are being disposed of in landfill. For both digestate and ash, their disposal means that nutrients are lost from the cycle, incurring high costs to the renewable energy industry. These limitations present a clear need for development of an alternative product or process which can present an attractive solution to both the bio-energy and agricultural sectors alike.The overarching objective is to develop commercially viable, high quality, consistent, sustainable fertilisers from bioenergy residues. Four main considerations are central to understanding the behaviour of the feedstocks in making a product: nutrient retention, form, and stability of the nutrient during processing; and whether the nutrient will be supplemented by other sources to meet a specification. Considering the aforementioned statements, the overall aim will be achieved through the following:(i) Physico-chemical characterisation of individual waste streams (ash and digestate) and putative fertiliser products, including the identification of other suitable wastes(ii) Assessment of the effects of reaction conditions on nutrient availability and potentially toxic elements presence on the fertiliser product, especially to understand in detail nitrogen retention, Phosphorus speciation and availability and long term stability controlling factors. (iii) Quantification of the impact of ash and digestate mixtures on plant growth and comparison against traditional inorganic fertilisers.(iv) Identification of legislative requirements and commercial considerations of the putative fertiliser products for use in agriculture as factual alternatives to conventional fertiliser applicationsExtensive testing on selected treatments and reaction conditions in the laboratory and plant growth in glasshouse trials will represent and step towards the applicability, commercialisation and viability of the formulated product in an agricultural setting. Benefits of such scenario are reduction in the dependence on phosphorus and nitrogen finite fertiliser resources, contribution to food security and compliance with waste hierarchy and resource recovery.