An investigation of the potential of anaerobically digested piggery waste for use in food production, with particular reference to tomato and fish production.

Watson, Nicholas R (1984). An investigation of the potential of anaerobically digested piggery waste for use in food production, with particular reference to tomato and fish production. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000f94f

Abstract

The purpose of this study is to investigate the potential of animal waste for use in food production, by employing anaerobically digested piggery waste as a nutrient source for tomatoes and fish.

The problem has been configured in terms of a "Bioplex" (integrated agriculture) system, and as such has been tackled by employing a bastardised systems methodology, which seeks to recognise the relationships between the resource to be used, and the food production system itself. This assumption underlies the experimental work carried out in the thesis.

Initial experimentation comprised studies on the use of the piggery effluent in its raw form as a medium for the hydroponic production of tomatoes by nutrient film technique, and as a conventional fertiliser. These trials, and a study of the physical and chemical characteristics of the piggery waste indicated that in order to maximise the food production potential of the effluent, it should be viewed as a composite of three different fractions, each of which may be most usefully employed in a specific food production system.

The bulk of the thesis is concerned with the extraction of two distinct fractions of the effluent; the protein rich suspended solids, and the aqueous phase, by means of an oxidation technique.

The main criterion used to describe the success of the separation process is the application of the two products to food production operations, rather than the efficiency of the separation per se. To this end, the clarified liquid, and the separated solids were used as the basis of a nutrient solution for the hydroponic production of tomatoes, and a substitute protein source in the diet of common carp, respectively. The separation technique passed through two design iterations before products suitable as nutrient sources were generated.

As the trials on fish and tomatoes were closely linked to the separation technique, this work occupies the main body of the thesis, and the initial feasibility experimentation is presented in the form of appendices.