Abstract
Throughout the world, agriculture, sanitation and waste management sectors are mainly carried out in isolation, resulting in permanent nutrient drainage and large amounts of greenhouse gas emissions due to inadequate or excessive use of fertilizers. Currently in Costa Rica, after a study of coffee waste treatment practices in conjunction with NAMA Coffee and based on previous studies carried out in the country, certain questions have arisen regarding the practices and management of coffee by-products to produce organic compost. During this study, a methodology to measure the impact of the application of an aerobic treatment technology for coffee by-products was developed and applied. With this method, different techniques of composting were compared regarding their emission of greenhouse gases, especially methane. As a next step, the reasons for the higher emission rates were examined. The emission rates are given in units of [g/m2 h] and the categorization and emission ranges were obtained according to the type of treatment and movement at the composting piles of each mill visited in the country. Moreover, ranges of emission factor in this article are given in g CH4/kg raw material. The duration of the project was from December 2017 until July 2018. In total 7 mills were visited in the country, divided in 4 cooperatives or mills and 3 private mills (small coffee farms). The methane emissions that have been observed during the different types of treatment applied to the coffee by-products indicate that the conditions must be optimized in order to create high-quality compost without any negative impact on the environment. The results obtained give an overview about five categories of treatment techniques that are used in Costa Rica to convert coffee by-products into compost which is used as a fertilizer. To some of these composting-categories, methane emission factors were calculated. It was found, that depending on the type of treatment, the methane emissions are between 10 times and more than 60 times higher than emission rates at garden waste or bio-waste composting plants referenced in literature. German Agency for International Cooperation (GIZ) established a NAMA support project (NSP): Low-carbon coffee Costa Rica. Within this framework, the actual activities are carried out.
Highlights
In recent years, composting has become a promising technique for degrading organic residues and producing fertilizer under low operating costs and technology [1]
During the period of measurements one of the mills was taken as a study area, in order to understand the behaviour of the temperature over the composting piles for the period of 5 weeks (Mill 1)
The following results are described and compared over time of composting treatment regarding the type of material added and the weeks of each pile available in the mill to proceed with the measurements during the harvest of 2017-2018
Summary
In recent years, composting has become a promising technique for degrading organic residues and producing fertilizer under low operating costs and technology [1]. Compost Systems can be divided in three different bases and depending on them, the classification can be done according to the oxygen usage (anaerobic and anaerobic), temperature (mesophilic and thermophilic) and according to the technology applied [4]. For this last base, the general classification of different composting systems can be done in two categories: “windrow or pile” ( open system) where the whole system is done in the open in elongated piles (windrows) and “in vessel” ( enclosed system) were the process is done in a reactor [4,5]. Regardless the type of system used in open windrow composting, even if there is a control or not of the exhaust gases produced during the process, windrow composting derivate a challenge for the quantification of the emissions [7]
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