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California Shell and Hull Waste to Energy Generating Biomass

California Shell and Hull Waste to Energy Generating Biomass

Written by Dr. Michael Lawrinenko

Our modern society and the conveniences we enjoy comes with a price as demand for energy, food, fiber, and fuel has been met with use of fossil fuels and the development of intense agricultural practices which the use of has generally led to detrimental effects on environmental quality. Landfills and waste yards that hold agricultural and municipal wastes abound our land. Despite some recycling efforts, often it is simply too expensive to eliminate many wastes or open burning is prohibited due to the negative impact on air quality. Trash to steam and co-generation energy plants can mitigate some waste, however it is often economically unfeasible to burn it all: high transportation costs and low-energy values make it too expensive to haul some wastes or even utilize materials that are too wet, do not combust well, and are too far away. As such, land is continually being reappropriated for dumping, substantial amounts of trash are dumped in the oceans, and there continues to be a lack for a sustainable way to manage waste that protects the air that we breathe, the water we drink, and the soil from which we eat.

Pyrolysis is a process in which biomass and wastes such as garbage, agroforestry residuals (wood chip, nut shells, etc.), and even manures are heated under low-oxygen conditions. Biological material is transformed to charcoal and gases. Biochar is charcoal specifically produced from biomass and was originally intended for soil application. However, biochar has many uses and has been developed for water treatment applications, air filtration, and some material production. While there is yet debate about the large-scale production of biochar for specific applications, the pyrolysis process can most definitely condense waste and offer a solution to the growing problem of waste accumulation. Further, the process destroys microbial and viral material-effectively sterilizing the waste as it is converted to charcoal.

The California Almond Board estimates almost 5.6 billion pounds of almond nut shells and hulls. Additionally, there are many other nutshell, pruning wastes, and forestry wastes that require costly grinding equipment and additional fossil fuel usage to operate-just to grind up these materials so they can be land applied. When economical, some of these wastes are burned at co-generation power plants, however the energy value is low (often less than half that of coal) and high transportation costs preclude utility of wastes more than 30 miles from the energy plant. Further, there exist tremendous quantities of non-recyclable paper and plastic wastes that are landfilled. These wastes can be diverted from landfills and from our oceans by converting them into higher energy charcoal with consistent energy value that would be more economical to then ship to co-generation power stations.

Energy values of most biomass are far less than that of coal. Oven dried wood is about two-thirds while fresh wood chips are about a third and baled grasses one fourth to one third that of coal. Charcoal can have energy values up to 90% that of coal. Yield of charcoal can range from 10 to 25%. Therefore, the mass of waste could be realistically reduced to one fourth when converted to charcoal that can be directly fed into co-generation power plants and provide the energy needed to drive these systems. As less mass is transported, the cost to transport charcoal in terms of its energy value would be roughly one fourth to one third that of transporting the biomass which would enable the utilization of biomass and other wastes that are currently too far from the power plant. Thus, using a system that converts wastes to charcoal onsite would create a win-win situation for California in diverting wastes from landfills and increasing green energy production.

Until recently, processes and equipment developed to pyrolyze materials have been costly and consume substantial energy. One of the biggest challenges to economic pyrolysis is moisture content of the feedstock. These challenges have been overcome with the recent development of a system by Dr. Michael Lawrinenko, a soil scientist and expert in biochar. With 450 citations on seven peer-reviewed journal articles, his passion for protecting the environment and deep interest in biochar sparked the interest in developing a pyrolyzer that is economical and robust. His professional work may be found on Google Scholar at https://scholar.google.com/citations?user=HalS7RAAAAAJ&hl=en  While still in development, this system can directly use wet biomass and convert it into biochar. This process is being developed using wood chips; some is fresh and some is compost. This pilot system utilizes a portion of the material for process heat; to drive the drying and pyrolysis of the remaining material. This important breakthrough could potentially be applied to convert agroforestry and other wastes in California for green energy production.