Processing of organic waste can improve its nutrient availability and content, and thereby increases the agricultural value of the waste when used as fertilisers, while contributing to a more bio-based, ‘circular’ economy. It is therefore important to guide future policies onwaste management and on the development of industries related to processing of organic wastes from agriculture, industry and households. However, there is a lack of understanding of the decision-making processes underlying the use of processed and unprocessed organic wastebased fertilisers by farmers.Weconducted a survey asking farmers in Denmark about their current use of organic fertiliser, their interest in using alternative types in the future, and their perception of most important barriers or advantages to using organic fertilisers.

A representative sample of farmers with >10 ha of land were sent a questionnaire; in total 452 responses (28% response rate) were received. Almost three quarters of respondents (72%) used organic fertiliser, and half of the arable/horticultural farms (without livestock) used unprocessed manures, suggesting significant manure exchange from animal production farms to arable farms in Denmark. Looking forward three years from the time of the survey, respondents did not expect to increase the amount of organic fertiliser they used. However, future interest in using processedmanures (PRO) and urban waste-derived fertiliser (URB) was greater than their use at the time of the survey (66% interest vs 19% current use of PRO and 32% vs 9% current use of URB). Anaerobically-digested slurry, acidified slurry, and composted/thermally-dried manure or slurry were products of particular interest. A large percentage (40%) of farmers did not have access to processed forms of organic fertiliser, particularly PRO (35% of respondents). Farm and farmer characteristics such as farming activity, farmer age, farm size, and conventional/organic farming influenced the likelihood of future interest in alternative organic fertilisers.

The most important barriers to the use of organic fertiliser identifiedamong respondentswere: unpleasant odour for neighbours, uncertainty in nutrient content, and difficulty in planning and use. Improved soil structure was clearly chosen as the most important advantage or reason to use organic fertiliser, followed by low cost to buy or produce, and ease of availability. Danish government policies aim to increase in manure processing (e.g. increasing anaerobic digestion for bioenergy recovery). A mix of industry and government-led measures could potentially increase availability
and farmer-use to meet these targets.

Case S., Oelofse M., Hou Y., Oenema O., Jensen L.S. (2017) Farmer perceptions and use of organic waste products as fertilisers – a survey study of potential benefits and barriers. Agricultural Systems 151, 84–95 (http://dx.doi.org/10.1016/j.agsy.2016.11.012)