https://www.researchgate.net/publication/268148367
Bonten, L.T.C., K.B. Zwart, R.P.J.J. Rietra, R. Postma and M.J.G. de Haas, 2014. Bio-slurry as fertilizer; Is bio-slurry from household digesters a better fertilizer than manure? A literature review. Wageningen, Alterra Wageningen UR (University & Research centre), Alterra report 2519. 46 pp.; 2 fig.; 9 tab.; 108 ref.
In many developing countries, animal manure is anaerobically digested, sometimes in combination with human excreta, to produce biogas, which is used for cooking and/or basic lighting. Besides biogas, anaerobic digestion produces a residue, the so-called digestate or bio-slurry, which contains most of the nutrients of the original manure, partially in a converted form. This bio-slurry can potentially be used as an organic fertilizer.
Numerous studies have been conducted on the comparative value of bio-slurry as a fertilizer or fish feed and its comparative value to farmyard manure. However, these studies do not provide a uniform message. The differences between the results of the studies can be due to several reasons, e.g. bio-slurry source, storage and handling, crop types, soil and climate conditions, or differences in methodologies to assess the value of bio-slurry as a fertilizer.