Filters
Loss of Energy and Economic Potential of a Biogas Plant Fed with Cow Manure due to Storage Time
The aim of the publication was to analyze investments in biogas plants with a cogeneration unit for an average size dairy farm. The basis for the calculation was the use of cow manure as the only substrate in methane fermentation. The economic balance also includes ecological and service aspects. The study also shows how much energy and quality potential is lost due to improper manure management and what impact a single farm with dairy cows has on the emission of carbon dioxide equivalent. It has been estimated that as a result of improper storage of manure, even 2/3 of its fertilizing, energy and economic value can be lost, while causing damage to the environment. It has been estimated that for a single farm with 100 cows, without government mechanisms subsidizing investments in RES, the payback period exceeds 15 years, and the Return of Capital Employed is slightly more than 6%.
The Biogas Potential of Oxytree Leaves
This article describes the characteristics of th Oxytree (Paulownia) plant, both in terms of its impact on GHG emissions and its potential use to produce biofuel, i.e., biogas. The described research involved the physico-chemical and elemental analysis of the Oxytree leaf composition and its biogas efficiency depending on the harvesting method. Three different scenarios were considered: the freshest possible leaves—processed immediately after stripping from the living tree; after the first day of collection from pruned or harvested wood; after the first week of collection from pruned or harvested wood. The best results were achieved for the harvest of the freshest leaves—on average 430 m3/Mg (biogas) and 223 m3/Mg (methane) per dry organic mass. The highest yield of biogas in terms of fresh mass (FM) was obtained for leaves fallen and collected after 1 day—123 m3/Mg FM, and 59 m3/Mg FM (methane). Processing Oxytree leaves through anaerobic digestion will contribute to reducing the carbon footprint of wood biomass production and is an additional source of renewable energy and fertilizer product.
Analysis of the Energy and Material Use of Manure as a Fertilizer or Substrate for Biogas Production during the Energy Crisis
The main goal of the publication was to show the differences in profit when using manure directly as fertilizer (after the storage period) or as a substrate for biogas plants with a cogeneration unit, and then using the digestate for fertilization purposes. The comparison covers the streams of costs, revenues and profits over the year between 14 October 2021 and 14 October 2022. This period was chosen due to the energy and fertilization crisis caused by the war in Ukraine. Profitability forecasts for biogas investments (including the payback period) are presented, with the reduction of greenhouse gas emissions, i.e., methane and nitrous oxide, taken into account. The performed economic, energy and ecological calculations of manure management can be used as guidelines when considering investing in biogas plants, as well as what is recently becoming a new trend: the carbon footprint of dairy production. Input substrate parameters, gaseous emissions and biogas yields were obtained from own research (manure samples were collected) and from literature data, including guidelines for international and national IPCC protocols.
The Impact of Manure Use for Energy Purposes on the Economic Balance of a Dairy Farm
The use of methane fermentation in mesophilic conditions for the energy use of cow manure and additional co-substrates from the farm can bring a small dairy farm (140 dairy cows) financial benefits of up to EUR 114,159 per year. Taking into account the need to pay for emissions calculated as carbon dioxide equivalent, this profit could be reduced to EUR 81,323 per year. With the traditional direct use of manure, this profit would drop by as much as 60% to the level of EUR 33,944 per year. Therefore, the introduction of fees for emissions may significantly burden current dairy farms. As has already been shown, just compacting and covering the manure (which costs approx. EUR 2000 per year for 140 cows) would give almost twice as much profit—EUR 64,509 per year. Although an investment in a small biogas plant with a cogeneration unit on a family dairy farm may have a payback period of less than 6.5 years and a return of capital employed of 16%, most small farms in the world will not be able to afford its construction without external subsidies. At the same time, it would make it possible to reduce emissions by almost 270 times—from 41,460 to 154 tons of CO2eq per year—and the possibility of preserving valuable nutrients and minerals and supporting soil properties in the digestate. Therefore, it seems necessary for Europe to introduce a support system for small- and medium-sized farms with this type of investment in the near future in a much larger form than it has been so far.