Polyethylene plastics
are a major source of industrial and household
wastes, the majority of which end up in the environment or in landfills.
These wastes pose challenges for microbial biodegradation due to their
polymeric structure. There is a critical need for a process that aids
in the breakdown and reuse of plastic compounds. Pyrolysis of high-density
polyethylene (HDPE) has previously been used to induce chemical changes
in plastic compounds, resulting in more structurally simplistic compounds.
Here, we demonstrate the ability of pyrolysis to produce microbially
biodegradable intermediate compounds. Biodegradation of pyrolysis-treated
plastics has not previously been demonstrated. We found that enrichment
cultures derived from six different environmental inocula were able
to achieve extensive biodegradation of polyethylene pyrolysis products
over the course of 5 days. We verified the biodegradation by quantifying
residual compound concentrations of alkenes using gas chromatography/mass
spectrometry (GC/MS). 16S rRNA gene amplicon sequencing results demonstrated
that the most dominant taxa in the microbial community belonged to
the phylum Proteobacteria. Many organisms in this phylum have previously
been shown to metabolize hydrocarbons. Our results indicate that the
coupling of chemical and biological processes can speed up the breakdown
and conversion of polyethylene to bacterial biomass by microbial consortia.
There has been an increasing interest in continuous base-load low-carbon renewable energy generation in the United States. Several technologies have been developed to convert biomass into energy, and anaerobic digestion is one such technology to convert food waste and animal manure into power by biochemical conversion and combustion. Many studies have looked at the optimization of the biomass supply chains in combination with environmental impacts. However, there are very few studies in the literature for determining the optimum location of biopower plants fed by food waste and manure. This study evaluates the optimum locations, sizes, and the number of plants for biopower production in Wisconsin using both mixed-integer linear programing and geographic information system network analysis (ArcGIS V10). The main objective of the study is to maximize the profits of biopower facilities accounting for both the profits from the biopower supply chain and carbon credits. In this study, two scenarios (base case and a future case) were evaluated by varying the carbon credits and the food waste tipping fee: the base case with $0 carbon credits and $0 food waste tipping fee and the future case with $15/ton CO 2 savings and $40 tipping fee/ton collected for the food waste. The key results showed that the inclusion of a carbon credit and tipping fee policies increased the profitability of biopower production and predicted an increase in biopower production capacity from 15 to over 77 MW in WI, representing 1% of its annual electricity consumption.
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