A simulation model of combined biogas, bioethanol and protein fodder co-production in organic farming

Anaerobic digestion based on animal manure and energy crops is very effective technology to provide energy and reduce green-house gasses emission, in particular ammonia and methane. Besides, utilisation of biogas contributes to reduction of CO2 emission. On the other hand, production of bioethanol from starchy or lignocellulosic materials can supply farmers with liquid fuel necessary for agriculture machinery. Therefore, there is a need for development an effective biorefinery for sustainable energy production in organic agriculture. Due to large amount of existing technologies and many ways for co-production of feed and fuel, the application of process engineering tools is required. The new innovative process configurations can reduce energy production costs and increase a sustainability of the organic farms. Through the development of integrated bioprocesses (biogas, bioethanol and protein production) and combining those different steps into a single unit, it will be possible to develop sustainable energy production at the single organic farm. A process-simulation model for 100 ha organic farm was developed in order to evaluate new strategies for production of renewable energy in sustainable agriculture. We developed simulation model using SuperPro Designer® software, it contains processing information like: composition of raw materials, flow rates of the various streams and description of the specific unit operations. The process includes feedstock handling and preparation, simultaneous saccharification and fermentation for ethanol production, anaerobic digestion for biogas production, protein separation and recovery, process water recirculation. Data for the development of the model was obtained from laboratory trials, literature data, expert’s consultancy, and results from BioConcens project (http://www.bioconcens.elr.dk). Different design approaches were evaluated in order to find the most suitable configuration. Clover grass, maize, rye, vetch, whey, and cattle manure were selected as raw materials for co-production of fuel and feed at the organic farm. Crops grown in organic agriculture were used as a key carbon sources whereas manure and whey were applied mainly as nutrients and process water supply for the fermentations (anaerobic digestion and simultaneous saccharification and fermentation, respectively). Results from batch and lab-scale fermentation trials were basic input for the model. For different energy crops biogas yield vary between 250 and 500mL of methane per gram of volatile solids. Theoretical ethanol yield based on glucose content in biomass i.e. for clover grass vary from 10 to 15g of ethanol per 100g dry biomass. The theoretical ethanol yield was measured both for dry and ensilaged clover grass, maize and rye. Several ways of storage and mild pre-treatment were investigated in a lab scale and evaluated in the simulation model. Different scenario can be simulated adequately to the farmer’s needs. Particular case can be adjusted to a specific organic farm. Based on the presented model, we are able to estimate the cost of renewable energy in organic farms for the most promising configurations

Biogas and Bioethanol Production in Organic Farming

The consumer demand for environmentally friendly, chemical free and healthy products, as well as concern regarding industrial agriculture’s effect on the environment has led to a significant growth of organic farming. On the other hand, organic farmers are becoming interested in direct on‐farm energy production which would lead them to independency from fossil fuels and decrease the greenhouse gas emissions from the farm. In the presented work, the idea of biogas and bioenergy production at the organic farm is investigated. This thesis is devoted to evaluate such a possibility, starting from the characterization of raw materials, through optimizing new processes and solutions and finally evaluating the whole on‐farm biorefinery concept with the help of a simulation software

Energy and emergy evaluation of potentials for energy self-sufficiency in Danish organic dairy farms by production of biogas and bioethanol

One obvious way to enhance agricultural resilience is for farms to increase self-sufficiency with necessities such as fuel, fodder and fertilizer. Our research seeks to uncover these potentials for Danish organic dairy farming. The setting is a theoretical model of a farm-cooperation of 10 farms of 100 ha each producing only milk and animals for slaughtering and being self-sufficient with fodder and fertilizer. The question is if they can be self-sufficient with energy by means of shared biogas and/ or bioethanol production facilities. The method is mapping of energy, emergy (embodied energy measured in solar energy joules) and mass flows in different scenarios, that are based on empirical data from Danish dairy farms concerning mix of crops, crop yields, livestock input/output and fuel and electricity consumption. In various scenarios different utilization of the produced crop is tested. Biogas is produced from manure and either clover grass or maize, and the effluent is fed back to the fields as fertilizer. In another scenario bioethanol is produced from grain and whey originating from the dairy cheese production, and the effluent is fed back to the livestock as a protein-rich fodder. Results compare the different scenarios in terms of mass, energy and emergy flows, thus including direct and indirect energy. Overall resource and energy efficiency are evaluated

Net-Energy Analysis of Integrated Food and Bioenergy Systems Exemplified by a Model of a Self-Sufficient System of Dairy Farms

Agriculture is expected to contribute in substituting of fossil fuels in the future. This constitutes a paradox as agriculture depends heavily on fossil energy for providing fuel, fodder, nutrients and machinery. The aim of this paper is to investigate whether organic agriculture is capable of providing both food and surplus energy to the society as evaluated from a model study. We evaluated bioenergy technologies in a Danish dairy farming context in four different scenarios: 1) vegetable oil based on oilseed rape, 2) biogas based on cattle manure and grass-clover lays, 3) bioethanol from rye grain and whey, and 4) a combination of 1) and 2). When assessing the energetic net-contribution to society from bioenergy systems, two types of problems arise: How to aggregate non-equivalent types of energy services, and how to account for non-equivalent types of inputs and co-products from the farming? To avoid the first type, the net output of liquid fuels, electricity, useful heat and food were calculated separately. Further, to avoid the second type, all scenarios were designed to provide self-sufficiency with fodder and fertilizer and to utilize co-products within the system. This approach resulted in a transparent assessment of the net-contribution to society, which is easy to interpret. We conclude that if 20% of land is used for energy crops, farm-gate energy self-sufficiency can be achieved at the cost of 17% reduction in amount of food produced. These results demonstrate the strong limitations for (organic) agriculture in providing both food and surplus energy

Production of microbial lipids utilizing volatile fatty acids derived from wastepaper: A biorefinery approach for biodiesel production

Volatile fatty acids (VFAs) derived from organic wastes are being considered as low-cost feedstock for microbial lipid production as a valuable alternative to plant derived oils/biodiesel. In this study, VFAs were produced from anaerobic open culture fermentation of wastepaper and subsequently, used as a feedstock for lipid production by Cryptococcus curvatus. Total VFAs, yield and productivity achieved from waste office paper (WOP) and waste newspaper (WNP) were 17.3 and 10.2 g/L, 0.17 and 0.10 g/g TS, and 0.86 and 0.51 g/L/day, respectively. Biomass, lipid content and productivity achieved utilizing VFAs derived from WOP and WNP were 4.3 and 2.9 g/L, 41.2 and 27.7% DCW, and 0.037 and 0.033 g/L/h, respectively. The dominance of fatty acids such as oleic, palmitic, stearic and linoleic acid in the lipids suggests a high level of similarity with plant/vegetable oils used for biodiesel production. Therefore, VFAs derived from wastepaper could be potentially used as feedstock to produce microbial lipids towards cost-effective production of biodiesel

BioConcens: Biomass and bioenergy production agriculture – consequences for soil fertility, environment, spread of animal parasites and socio-economy

The research programme called “international research cooperation and organic integrity” was commenced for a period 2006-2010. It is coordinated by DARCOF (The Danish Research Centre for Organic Farming). The whole programme, with acronym DARCOF III, consists of 15 projects (http://www.darcof.dk/research/darcofiii/index.html). One of them is BIOCONCENS - Biomass and bioenergy production in organic farming – consequences for soil fertility, environment, spread of animal parasites and socio-economy (http://www.bioconcens.elr.dk/uk/). The production of bioenergy in organic agriculture (OA) can reduce its dependency of fossil fuels and decrease green house gasses emission; consequently it will increase sustainability of organic farms. Biorefinery concept based on co-production of biogas, bioethanol and protein fodder in organic farming will be developed within the BIOCONCENS project and the background for the project and the different work packages will be presented in this paper