An integrated innovative project for sustainable production of bioethanol, methane and compost from sweet potato
Because of shortage and cost of fossil petrol, there is a continuous research for alternative energy sources.
Utilizing agricultural crops it must be very important not to interfere with those products which are utilized for human feeding. The risk will be an increase of their cost, as it recently happened in U.S.A with corn and wheat. In this project sweet potato, from a germoplasm, genetically selected by the Chinese Academy of Sciences in Shanghai, resistant to salty soils, will be used. These sweet potatoes therefore will not interfere with human or animal feeding because they will grow in Chinese salty soils not suitable for other agricultural crops.
This plant is an innovative integrated project for the sustainable production of bioethanol, methane and compost. The starch of sweet potato, by hydrolysis and fermentation will produce bioethanol; the by-products of this process, with other part of the plant (leaves, skin, fibers) will be utilized as starting material in Anaerobic Digestion, producing methane. Sludge from anaerobic digestion will be composted, after appropriate conditioning, and utilized as fertilizer in the soils where sweet potato is grown. This organic fertilizer, produced with adequate systems, will be suppressive to phytopathogenic agents of sweet potato. It will reduce, therefore, not only the use of chemical fertilizers but also of pesticides, products which both come from petrol energy.
This integrated industrial plant does not produce any waste, recycling all the by products, including the water used in the processes, and does not need any thermal and electric energy from external sources, because these are produced by transformation of methane into energy. Only 20% of the electric energy produced is utilized to feed the plant, the remaining 80% is sold in the net.
This plant is therefore sustainable, utilizing and producing energy from renewable sources, and, in accord with Kyoto protocol, reduce the CO2 emission in atmosphere. The main characteristics of the proposed plant are:
1. High quantity and quality of bioethanol (99.99%), produced with innovative technologies at lower costs and without interfere with human food production.
2. Sustainable process not utilizing energy coming from petrol and not producing waste, recycling all the by products coming from the industrial processes.
3. No air, water and soil pollution.
4. Economical benefits in agriculture and at industrial level: lower production costs and higher income because of high energy recovery and no waste production.
5. Reduction of CO2 emission in atmosphere (carbon credits).
6. Preserving the biological fertility of soils where sweet potato is grown, recycling organic matter and nutrients as compost which is produced from renewable energy.
7. Compost utilization will guarantee a constant production of sweet potato in the years and therefore a constant production of bioethanol, reducing also the use of chemical fertilizer and pesticides.
