Sustainable cost reductions: biogas from liquid wastes
More and more dairies are now facing a problem: how to dispose of their liquid waste products. Spreading slurry is not a realistic option any more for the agricultural industry due to the problems of overfertilisation or hygiene. The challenge for dairies is that their liquid waste products generally have a very high organic load. Wastewater accumulates, typically, as a result of cleaning and rinsing processes in production. Local rural treatment plants where most dairies are located are not designed to cope with such high organic loading.
EnviroChemie is working with a large dairy in Morocco which is part of an international food group to find an alternative route: instead of disposing of all the liquid waste, the company is turning it into biogas. To achieve this, EnviroChemie has installed an anaerobic Biomar bioreactor, metabolising the liquid waste and resulting in methane (CH4), i.e. biogas, and carbon dioxide (CO2).
The anaerobic process saves more energy than aerobic processes. The highly loaded wastewater flow from production is pretreated separately in the anaerobic reactor. This reduces the load on the aerobic wastewater treatment process, saving energy for the aeration of the aerobic biological mass. In general, this reduces electricity consumption by up to 30 per cent.
Furthermore the biogas can be used as an energy source. The dairy in Morocco uses it to produce steam to heat and pasteurise the milk. The dairy reduces its oil consumption by approximately 30 per cent. However, there is still a certain amount of solid residue and liquid waste at the end of the process, but overall it is significantly less. The dairy is therefore not only reducing the load on their wastewater plant but also making considerable savings in terms of disposal costs.
EnviroChemie’s experts conducted a series of comprehensive tests and studies in advance in order to develop the best solution for the dairy and to explore the limits of the system. Following this, they suggested not only feeding in the whey from the main production into the Biomar bioreactor but also using other products as well, such as the floatation sludge and the sludge from the existing biological treatment plant. In addition to approximately 80 cubic metres of whey, around 160 cubic metres of other liquid waste are also added. Up to 12 cubic metres of returned product and exhausted milk is also used a day.
EnviroChemie has manufactured the plant in Germany and delivered it as complete modules. In many cases, this overcomes specific issues with building legislation or environmental regulations and reduces the build time on site.
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