ObjectivesThe proposed program aims in developing a new biotechnology method for production of a physiologically active plant growth media from instant coffee waste, thus solving the ecological harm caused by the wastes. Specific objectives envisage the optimization of the Anaerobic Methanogenic Thermophilic Digestion (AMTD) process of solid instant coffee waste and examination of all aspects in a pilot plant scale.AbstractIn the process of producing "instant coffee", large quantities of relatively solid waste (20% solids) are left, and have to be carted from the factory and dumped, at considerable expense, causing ecological harm to the area by polluting ground water. Several solutions and alternative uses of the coffee wastes have already been examined (as fertilizers, livestock feed, compost) without giving economically viable results.
The aim of this project was to develop Biogas technology for the ecological and economic treatment of coffee wastes, and the evaluation of the digested material as a growth medium for horticulture. A key factor in planning for an appropriate technology is that it has to focus on the integration of the Biogas plant into the existing infrastructure of the factory. The study consisted of anaerobic, methanogenic, thermophilic digestion (AMTD) of solid coffee wastes in laboratory scale digesters and also in a small (3x300 Liter) pilot plant system. Optimal conditions for the process in loading rates, retention time, solids’ concentration and chemical parameters were examined. The results of these experiments showed that digestion of instant coffee waste is a feasible process, not requiring addition of nitrogen, nor prior grinding of the coffee waste, though pH control was necessary. Furthermore, for a continuous system adapted to coffee waste, the growth phase of bacteria to achieve maximal colonization, is necessary. For feeding of coffee waste (which is an inhibitory environment to bacteria) into the digestion system at high loading rates, the operating conditions were tailored. The inhibitory effect depends on the properties of the intermediate compounds, and can be controlled by operating conditions, such as volumetric flow rate of the feed, the concentration of pollutant solids or by the addition of buffering agents. The continuous anaerobic digestion process can achieve a steady state of fermentation at relatively high loading rates. The products of the process are “Capul” – the digested slurry, and Biogas – a mixture of Methane and Carbon Dioxide gases.
The overall qualities of the digested slurry ("Capul") were determined, with a view to their suitability for horticulture. Clear acceleration of rooting and better development of root systems were observed with growth media containing from 50 to 75% v/v of digested coffee waste. Growth promotion effects on Phlox plants were found, as well as a positive effect on the sprouting of rootlets in Lysimachia fontuni. Furthermore, without auxin supplements, fermented solids induced rooting in Mung bean plants, similar to plant growth factor indole-3-acetic acid (IAA). We found indications that the fermented solids promoted rooting of otherwise difficult-to-root plants.
It was shown that the suppression of soilborne pathogens due to competition for available carbonaceous nutrient in compost and peat container media and suggested that this is the reason for the inhibition effect of Pythium growth, found in the use of the coffee waste material after digestion as soil media for growing plants. We want to emphasize that the biological digestion of the pollutant compound leaves a peat-like material, which is the main product of the process.
Taking into account the benefits of treating instant coffee wastes, (a) in solving the need to transport and dump the waste from the factory, at considerable expense; (b) the income to the factory from using the Biogas as alternative energy for its steam system; (c) selling the digested slurry ("Capul") to greenhouses, (the main income from the process), the process looks very attractive from an economic point of view. The AMTD process developed will therefore contribute to the solution of both economic and ecological problems of instant coffee wastes. New look at the production processFor industry to be ecologically sustainable in the long run, production processes must be developed, that use the entire input and which have no eco-systemic effects. In other words, total input must equal total output, achieving what is termed “total throughput”.
What is needed is a fundamental re-thinking of existing production and consumption models, and a new approach to the production of instant coffee. This is presented in Fig. 1. | 
