The enormous increase in the quantum and diversity of waste materials generated by human activity and their potentially harmful effects on the general environment and public health, have led to an increasing awareness about an urgent need to adopt scientific methods for safe disposal of wastes. While there is an obvious need to minimize the generation of wastes and to reuse and recycle them, the technologies for recovery of energy from wastes can play a vital role in mitigating the problems. Besides recovery of substantial energy, these technologies can lead to a substantial reduction in the overall waste quantities requiring final disposal, which can be better managed for safe disposal in a controlled manner while meeting the pollution control standards.

Waste generation rates are affected by socio-economic development, degree of industrialization, and climate. Generally, the greater the economic prosperity and the higher percentage of urban population, the greater the amount of solid waste produced. Reduction in the volume and mass of solid waste is a crucial issue especially in the light of limited availability of final disposal sites in many parts of the world. Although numerous waste and byproduct recovery processes have been introduced, anaerobic digestion has unique and integrative potential, simultaneously acting as a waste treatment and recovery process.

Waste-to-Energy Conversion Pathways

A host of technologies are available for realizing the potential of waste as an energy source, ranging from very simple systems for disposing of dry waste to more complex technologies capable of dealing with large amounts of industrial waste. There are three main pathways for conversion of organic waste material to energy - thermochemical, biochemical and physicochemical.

Thermochemical Conversion
Combustion of waste has been used for many years as a way of reducing waste volume and neutralizing many of the potentially harmful elements within it. Combustion can only be used to create an energy source when heat recovery is included. Heat recovered from the combustion process can then be used to either power turbines for electricity generation or to provide direct space and water heating. Some waste streams are also suitable for fueling a combined heat and power system, although quality and reliability of supply are important factors to consider.

Thermochemical conversion, characterized by higher temperature and conversion rates, is best suited for lower moisture feedstock and is generally less selective for products. Thermochemical conversion includes incineration, pyrolysis and gasification. The incineration technology is the controlled combustion of waste with the recovery of heat to produce steam which in turn produces power through steam turbines. Pyrolysis and gasification represent refined thermal treatment methods as alternatives to incineration and are characterized by the transformation of the waste into product gas as energy carrier for later combustion in, for example, a boiler or a gas engine.

Biochemical Conversion
The bio-chemical conversion processes, which include anaerobic digestion and fermentation, are preferred for wastes having high percentage of organic biodegradable (putrescible) matter and high moisture content. Anaerobic digestion is a reliable technology for the treatment of wet, organic waste. Organic waste from various sources is composted in highly controlled, oxygen-free conditions circumstances resulting in the production of biogas which can be used to produce both electricity and heat. Anaerobic digestion also results in a dry residue called digestate which can be used as a soil conditioner.

Alcohol fermentation is the transformation of organic fraction of biomass to ethanol by a series of biochemical reactions using specialized microorganisms. It finds good deal of application in the transformation of woody biomass into cellulosic ethanol.

Physico-chemical Conversion
The physico-chemical technology involves various processes to improve physical and chemical properties of solid waste. The combustible fraction of the waste is converted into high-energy fuel pellets which may be used in steam generation. Fuel pellets have several distinct advantages over coal and wood because it is cleaner, free from incombustibles, has lower ash and moisture contents, is of uniform size, cost-effective, and eco-friendly.

Article © www.alternative-energy-news.info Picture © The PFM Group
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More than 500 people gathered Monday for the State of Green Business Forum in San Francisco, an all-day event that marked the release of the State of Green Business 2009 report from the editors of GreenBiz.com. The report attempts to measure the adoption of green business practices in the U.S.

The Forum featured more than a dozen industry leaders to bring various aspects of the report to life: water management, green jobs, innovation and energy efficiency. GreenBiz.com Executive Editor Joel Makower also assembled a panel of advisors of President Barack Obama to discuss the new administration and its efforts to jumpstart a green economy.

In opening up the forum, Makower presented an overview of the finding of this year's report: in a nutshell, companies are doing OK, but there's plenty of room for improvement.

"Is all of this green activity we read about actually moving the needle?" Makower asked. "The answer, in aggregate, is not so much."

In running down a list of latest news stories, Makower offered examples of corporate environmental successes, all occurring since Nov. 4, 2008. Among them are beverage companies committing to grow their sales without using more water to make products, an apparel company incorporating green design principles into all its products, an IT company that developed energy management tools to dramatically cut companywide energy use, and a consumer products company selling $20 billion in greener products.

Despite the green success stories, the details of the State of Green Business Report are a mixed bag, but that progress is much slower than what we need. Makower outlined eight of the 20 indicators in the report that highlighted the good, the bad and the neutral in green business practices.

Among the sinking indicators Makower discussed were electronic waste and carbon intensity; in both cases companies in the U.S. are making slight improvements -- in total electronics taken back for recycling and the amount of CO2 equivalent generated per dollar of economic activity, respectively -- but that those improvements are failing to outpace the growth of the problems at hand.

On the more promising side, energy efficiency and paper use are areas in which U.S. businesses are swimming along well: "Energy efficiency is back on the table," Makower explained in looking at the long and steady decline in the amount of energy needed to power the economy year after year. In looking over the trends of the last few years, Makower said he expects that improved energy efficiency is something he expects to see as part of the discussion in businesses nationwide for years to come.

Article © GreenBiz

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Seminar: Building Green: Making Your Home More Energy Efficient

Join Design Forward's Lisa Swan in Glendale on May 30, 2009 for a Building Green seminar for home owners.

Class Description: Whether you are interested in a new house, remodeling your existing home, or just adding a few sustainable features, this innovative class will give you an in depth review of green building and sustainable architecture. Learn about solar and wind energy, wall systems such as straw bale, insulated concrete forms and foam insulation, natural and recycled materials, efficient windows and appliances, and more. Also learn how you can save money through State and local rebates.
Reference Class: SI011

Instructor: Lisa Swan is the owner of Design Forward, a residential design firm, specializing in sustainable and green projects. She is an Honors' graduate of the Illinois Institute of Technology, with a Bachelor of Architecture and has an MBA from Norwich University.

Date & Time: May 30, 2009 9:30am - 12:30am

Cost: $35, plus $10 materials fee is payable to the instructor in class.

Location: Glendale, CA - Garfield Campus of the Glendale Community College

Register Begins March 1, 2009: http://www.glendale.edu/cse

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Happy Birthday! March 1, 2009 marks Design Forward's 7th year in business. We want to thank everyone who has supported us so far. We look forward to continuing our work in the sustainable and green community for many more years.

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