Mixed plastics waste valorization through tandem chemical oxidation and biological funneling

115 p.-4 fig.-45 fig. supl.-14 tab supl.Mixed plastics waste represents an abundant and largely untapped feedstock for the production of valuable products. The chemical diversity and complexity of thesematerials, however, present major barriers to realizing this opportunity. In this work, we show that metal-catalyzed autoxidation depolymerizes comingled polymers into a mixture of oxygenated small molecules that are advantaged substrates for biological conversion. We engineer a robust soil bacterium, Pseudomonas putida, to funnel these oxygenated compounds into a single exemplary chemical product, either b-ketoadipate or polyhydroxyalkanoates. This hybrid process establishes a strategy for the selective conversion of mixed plastics waste into useful chemical products.Funding was provided by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office (AMO), and Bioenergy Technologies Office (BETO). This work was performed as part of the BOTTLE Consortium and was supported by AMO and BETO under contract no. DE-AC36- 08GO28308 with the National Renewable Energy Laboratory (NREL),operated by the Alliance for Sustainable Energy, LLC. The BOTTLE Consortium includes members from MIT, funded under contract no. DE-AC36-08GO28308 with NREL. Contributions by S.S.S. were supported by the US Department of Energy, Office of Basic Energy Sciences, under award no. DEFG02-05ER15690.Peer reviewe

Recovery of low molecular weight compounds from alkaline pretreatment liquor via membrane separations

Lignin is an abundant renewable resource that is a promising substrate for upgrading to fuels and chemicals. However, lignin-rich biorefinery streams are often physically and chemically complex, and could benefit substantially from fractionation. In this work, a membrane process was developed to fractionate low molecular weight (LMW) lignin-related compounds (molecular weight (MW) < 1000 Da) from a lignin-rich, alkaline pretreated liquor (APL) prepared from pretreatment of corn stover with NaOH. The developed membrane process exhibits up to 98.5% rejection of high molecular weight (HMW) (MW > 1000 Da) species and generates a permeate stream with >80% recovery of LMW lignin-related compounds including aromatic species such as p-coumarate and ferulate, resulting in a 6-fold enrichment in LMW organic compounds relative to the crude APL. Experimental batch data were used to develop a detailed process model of an industrial scale, continuous membrane filtration system. The open-source model has several independent process inputs, such as the concentration of target compounds, feed flow rate, volume recovery, and membrane selectivity. This process model was used to show that the system has a low estimated energy demand (0.75 kW h m−3 permeate) and was used to identify primary cost drivers, including the membrane material cost. These results offer a key step towards a scalable, low energy, and cost-effective lignin MW fractionation method with implications for both improving product isolation from lignin and improving carbon yields across the biorefinery