A holistic management approach: assessing the sustainability of aquaponics systems using biodigestate as partial alternative nutrient source
Date
2018-03
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH SUMMARY: One of the hurdles facing sustainable agricultural practice is the declining soil fertility that results from consistently cropping the same parcel of land and the demand of plants on especially mineral elements, which are often not sufficient for sustaining yields. In rural areas, this is exacerbated by the lack of various resources like knowledge, skills, infrastructure and equipment, limiting yield, quality or sustainability. In a water scarce country, the availability and use of this resource to optimize food production is another key point as varying climatic conditions have a greater impact on smallholder farmers that lack the resources, infrastructure, skills and knowledge to provide sustainable yields year upon year. The cost of fertilizers for higher production coupled to the cost to the environment by using only inorganic fertilisers is mounting. The search for alternative sources for nutrient supplementation in crops is a critical one that has not to date yielded a solution that is both environmentally and economically sustainable. The current project addresses the use of an alternative nutrient source, the by-product of anaerobic digestion of fruit and dairy feedlot waste in an aquaponics system compared to a conventional system which will utilize a conventional inorganic nutrient solution and municipal water, as a model to address the declining soil fertility and yield reduction as well as food security under conventional agricultural land based production.
Objectives
The overall objective of this study was to:
1) Identify an anaerobic digester facility as a source for nutrient rich digestate for plant growth in RAS aquaponics. It was also imperative to as well as a source of recycled water.
2) Quantify water quality parameters and selectively manipulate it accordingly to allow plants and fish to survive and grow. Plant species must be selected for the adaptability thereof in hydroponic culture conditions. The latter with specific dissolved nutrient availability and constitution to be identified. The plant species must also function acceptably as a source produce.
3) Identify a biofilter for the remediation of recycled water. The selected fish species must have viable hardy enough to grow in this medium and with an economic potential and be hardy enough to grow and consistently provide biofilter processed soluble nutrients for the aquaponic culture medium in the market.
4) Identify a plant species that can be grown hydroponically under these nutrient conditions and that could be used to evaluate the viability and function as a bio-filter to clean water for further use.
5) Lastly the best option for fish in this system that will allow marketing of the final product as well as be a bio-filter to purify water for recirculation was determined.
The hypotheses of the study were therefore that:
Digestate can be utilised as alternative nutrient source in an aquaponic system;
H0: Digestate is not suitable as alternative nutrient source for aquaponic plants.
Biofilter
Biofilter digestate as a suitable medium for fish growth in an aquaponic system:
H0: Digestate is not a suitable medium for the growth of plants and fish in an aquaponic system
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar
Description
Thesis(MScAgric)--Stellenbosch University, 2018.
Keywords
Aquaponics, Soil fertility, Anaerobic digester, Biofilter, Biofertilizer, Water -- Anaerobic treatment, UCTD