March 8-13, 2009
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.
Piotr Oleskowicz-Popiel, "A simulation model of combined biogas, bioethanol and protein fodder co-production in organic farming" in "Bioenergy - II: Fuels and Chemicals from Renewable Resources", Dr. Cedric Briens, ICFAR, University of Western Ontario, Canada; Dr. Franco Berruti, ICFAR, University of Western Ontario, Canada; Dr. Muthanna Al-Dahhan, Washington University, USA Eds, ECI Symposium Series, (2009). http://dc.engconfintl.org/bioenergy_ii/26