"Green engineering" is based on the idea of designing, selling and using processes and products that are technically and economically viable while, at the same time, minimizing pollution, as well as health and environmental risks. This is expressed in twelve principles that were formulated nearly a quarter of a century ago by the United States Environmental Protection Agency, and which the engineering and research firm Demede Engineering & Technology attempts to apply in all of its work. Its most recent development, a pilot plant for the anaerobic digestion of organic waste that was commissioned by the Universidad de Cadiz, is going to be used for research in the field of biogas production using wastewater, sludge and organic waste from landfills and purification plants.
The system is based on the biological processing that certain bacteria perform in conditions that lack oxygen, which convert organic waste material into a mixture of combustible gasses (carbon monoxide, hydrogen and methane). These gasses can be accumulated and later used in the production of heat and electrical energy. "This prototype will serve to optimize the processes that make use of waste material to produce energy and will be a useful instrument for solving the problem of managing potentially toxic wastes in urban, agricultural and livestock areas", explains the company's director of engineering, Javier Roa Fresno.
In order to design this prototype, it was necessary to form a multi-disciplinary team of experts in process and control engineering, mechanical engineering and electronic engineering, among others. For this project, their objective was to design a plant with the greatest operating efficiency, most economical processing, best waste reduction and easiest maintenance. "We have been working on the design o similar equipment for four years and this last project was carried out in approximately six months," state sources from the company, who are currently preparing an offer to provide similar systems to national and international clients; the systems would be for the treatment of agricultural and aquaculture waste, as well as for the treatment of sludge and mud from water purification plants.
The main reactor of this pilot plant consists of a stirred tank reactor in which the temperature and PH are controlled. The way it works is relatively simple: organic systems are continuously introduced and, as the biogas is produced by the metabolism of the microorganisms, the waste that is obtained is extracted through the lower part of the tank. "Since the equipment is used for R+D at the university, it includes some additional equipment that makes the process more versatile," comments Javier Roa Fresno. "The ultimate goal is to develop the technology and optimize the processes that lead to energy production on an industrial scale, using organic waste," he concludes.
Nanotechnology and chemistry
The company is exploring new projects in the field of nanotechnology, in collaboration with NanoInnova Technologies, in the search for new products derived from the production and modification of graphene, using sustainable synthetic routes, the development of mechanochemical activation and the use of supercritical CO2. In addition, Demede is also collaborating with Synthelia Organics, in the pharmaceutical field, to develop flow reactors for processes used in the production of medications and other intermediate compounds at high temperatures and under high pressure. In both cases, say the heads of the company, these projects are providing new products in the field of nanotechnology and the chemical industry, which are of high added value, and with the advantage that these products are being produced using new processes that minimize the generation of waste products and energy consumption, while maximizing the productivity and efficiency of old production systems.
The Business Incubator in the UC3M Science Park has supported this company since its birth, giving it access to its facilities and providing it with specialized consulting in the area of innovation. "Thanks to this effort, we have been able to increase our billing, gain market share with new clients and products, and continually add new members to our staff," comment the heads of Demede Engineering & Research. Their staff is made up of engineers (industrial and chemical) and technicians (mechanical and electronic), as well as of students from UC3M who are doing internships and working on their final projects for their degrees.
The 12 principles of green engineering, a code of best practices for design:
- Designers need to strive to ensure that all materials and energy inputs and outputs are as inherently nonhazardous as possible.
- It is better to prevent waste than to treat or clean up waste after it is formed.
- Separation and purification operations should be designed to minimize energy consumption and materials use.
- Products, processes, and systems should be designed to maximize mass, energy, space, and time efficiency.
- Products, processes, and systems should be "output pulled" rather than "input pushed" through the use of energy and materials.
- Embedded entropy and complexity must be viewed as an investment when making design choices on recycle, reuse, or beneficial disposition.
- Targeted durability, not immortality, should be a design goal.
- Design for unnecessary capacity or capability (e.g., "one size fits all") solutions should be considered a design flaw.
- Material diversity in multicomponent products should be minimized to promote disassembly and value retention.
- Design of products, processes, and systems must include integration and interconnectivity with available energy and materials flows.
- Products, processes, and systems should be designed for performance in a commercial "afterlife."
- Material and energy inputs should be renewable rather than depleting.
Explore further: More profitable biogas production by optimization of anaerobic waste digestion
Anastas, P.T., and Zimmerman, J.B., "Design through the Twelve Principles of Green Engineering", Env. Sci. and Tech., 37, 5, 94A-101A, 2003.