Gero Leson

BIOFILTRATION: AN INNOVATIVE AIR POLLUTION CONTROL TECHNOLOGY FOR VOC EMISSIONS

Biofiltration is a relatively recent air pollution control (APC) technology in which off-gases containing biodegradable volatile organic compounds (VOC) or inorganic air toxics are vented through a biologically active material. This technology has been successfully applied in Germany and The Netherlands in many full-scale applications to control odors, VOC and air toxic emissions from a wide range of industrial and public sector sources. Control efficiencies of more than 90 percent have been achieved for many common air pollutants. Due to lower operating costs, biofiltration can provide significant economic advantages over other APC technologies if applied to off-gases that contain readily biodegradable pollutants in low concentrations. Environmental benefits include low energy requirements and the avoidance of cross media transfer of pollutants. This paper reviews the history and current status of biofiltration, outlines its underlying scientific and engineering principles, and discusses the applicability of biofilters for a wide range of specific emission sources.

Evaluating Design Options for Biofilters

Abstract Biofilters are now increasingly offered and accepted in North America for air pollution control. However, prospective buyers often lack the technical and economic criteria to select a suitable biofilter design for their applications. This paper summarizes past experiences with full-scale biofilters and emerging design trends. Since control of the filter media’s moisture content is essential for effective pollutant removal, the processes affecting moisture content are reviewed and ranges for evaporation rates and dry-out periods are estimated. High VOC concentrations and elimination rates cause high moisture removal and require additional irrigation; excessive irrigation or condensation of moisture from hot off-gases routinely cause over-watering and poor performance. Consequently, an application’s moisture balance should be evaluated carefully prior to selecting a biofilter design. High VOC loadings and the need for low maintenance and verifiable pollutant removal favor fully enclosed vessels wit...

Biofiltration of High Loads of Ethyl Acetate in the Presence of Toluene

To date, biofilters have been used primarily to control dilute, usually odorous, off-gases with relatively low volatile organic compound (VOC) concentrations (< 1 g m-3) and VOC loads (< 50 g m-3 hr-1). Recently, however, U.S. industry has shown an interest in applying biofilters to higher concentrations of VOCs and hazardous air pollutants (HAPs). In this study, the behavior of biofilters under high loads of binary VOC mixtures was studied. Two bench-scale biofilters were operated using a commercially available medium and a mixture of wood chips and compost. Both were exposed to varying mixtures of ethyl acetate and toluene. Concentration profiles and the corresponding removal efficiencies as a function of VOC loading were determined through frequent grab-sampling and GC analysis. Biofilter response to two frequently encountered operating problems--media dry-out and operating temperatures exceeding 40 degrees C--was also evaluated under controlled conditions. Microbial populations were also monitored to confirm the presence of organisms capable of degrading both major off-gas constituents. The results demonstrated several characteristics of biofilters operating under high VOC load conditions. Maximum elimination capacities for ethyl acetate were typically in the range of 200 g m-3 hr-1. Despite the presence of toluene degraders, the removal of toluene was inhibited by high loads of ethyl acetate. Several byproducts, particularly ethanol, were formed. Short-term dry-out and temperature excursions resulted in reduced performance.

Hemp Foods in North America: Status and Joint Industry Research

Abstract In 2005, hemp acreage in Canada has doubled to 8,000 ha, driven almost entirely by the growing demand for hemp foods and cosmetics in the North American market for natural products. To sustain that growth, members of the Canadian Hemp Trade Alliance (CHTA), which represents all relevant industry sectors, have initiated a comprehensive R&D and communication program on hemp foods. Its main goals are to comprehensively characterize the nutritional profile of seeds, nuts, oil and flour, across all commercially relevant hemp varieties grown in Canada, to assess the relevance of the established profiles to nutritional health, and to communicate results effectively to trade journalists and consumers. Initial characterization studies will assess amino acids and fatty acids, minerals, vitamins, and select phytochemicals. Subsequently, a panel of experts on nutritional health will assess the data and project potential health benefits. In a related project, the impact of processing and storage conditions on rancidity will be quantified and quality management strategies will be developed. The overall joint R&D agenda is funded by several Canadian government programs and by industry contributions.

Evaluating the Impact of THC in Hemp Foods and Cosmetics on Human Health and Workplace Drug Tests

Abstract In recent years, the presence of trace residual delta-9-tetrahydrocannabinol (THC) in food and cosmetics from hemp seed and seed derivatives (oil, hulled seed) has raised concerns over THCs potentially adverse impacts on human health and on the results of workplace drug tests for marijuana. Two desktop studies and one experimental study were conducted to evaluate whether (1) the ingestion of high amounts of foods containing properly cleaned hemp seeds or their derivatives could cause psychoactivity or other undesirable impacts on human health, (2) the ingestion of these hemp foods may produce sufficiently high urine levels of THC metabolites to cause positive urine tests for marijuana and (3) the extensive use of hemp oil cosmetics may cause, or contribute to adverse health effects or a positive urine test. This paper provides an overview of these studies and presents their results and conclusions. In summary, the studies suggest that, at the levels now typical in Canadian hemp seed, THC in hemp foods and cosmetics does not cause unintentional psychoactivity, other adverse health effects or confirmed urine tests for marijuana. These levels provide protection from such effects with a wide margin of safety, even for individuals who consume hemp foods and cosmetics frequently and extensively.