BIOSLURRY = BROWN GOLD?

Bogdanski, Anne
Groot, Lennart de

2013

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In recent years, there has been an increasing interest in anaerobic digestion of farm and household residues in many parts of the world. Smallholder biogas digesters and community biogas plants can be found all throughout Asia, but also progressively in LatinAmerica and Africa. Anaerobic digestion produces two main outputs: biogas and bioslurry, the digestate or digester effluent. While biogas is used to produce energy, the large potential of bioslurry has often been overlooked. A large part of both the scientific and grey literature focuses on the production of energy alone, but does not venture into the multiple uses and intricacies of bioslurry use. Technical organizations such as NGOs, extension services and local universities and, last but not least, smallholders themselves, are often not fully aware of the multiple benefits of bioslurry use, nor do they know of the risks associated with handling and applying it on their farm. This review therefore attempts to synthesize the findings of the growing peer-reviewed literature on bioslurry to provide a sound and scientific basis for bioslurry use. At the same time, it sets out to identify the various research gaps. The majority of research has been conducted on the effect of bioslurry use on different soil structure and fertility parameters as well as on biomass and crop yield compared to the use of other organic fertilizers, or to the application of synthetic inputs. While, in general, it can be stated that bioslurry has proven to have positive effects on yields of grains, vegetables and fruit compared to not using any soil amendments and fertilizers at all, the comparison with other organic fertilizers such as undigested farm yard manure or compost, and with synthetic fertilizers like urea, remains very ambiguous. The results vary widely between different experimental designs. In some cases bioslurry outperforms synthetic or other organic fertilizers, in others it is the other way round. These results are not surprising, however, if one considers the varying nature of bioslurry in terms of organic matter and nutrient content, the characteristics of different types of soil and the nutritional requirements of different crop species. Only two studies examined the impacts of bioslurry on crop quality in terms of the amount and the variety of proteins and macro and micronutrients, which proved to outperform conventional fertilizers…

Biogas; Biolodo; Biomasa; Nivel mundial;