Anaerobic Codigestion of Food Waste and Polylactic Acid: Effect of Pretreatment on Methane Yield and Solid Reduction

Hobbs, Shakira R.; Parameswaran, Prathap; Astmann, Barbara; Devkota, Jay; Landis, Amy E.

doi:10.1155/2019/4715904

Cited by 45 publications

(29 citation statements)

References 31 publications

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“…Given their rapid market growth, understanding solid state enzymology can lead to immediate technological impact toward single use plastics. [28][29][30] However, enzymatic modifications of chemically dormant molecules, such as hydrocarbons and/or polyolefins, require synchronization of multiple biocatalytic processes and are slow even under biologically optimized conditions. 31 Without knowing how microbes modify and degrade polyolefins, 15,21,32,33 understanding how embedded enzymes behave will guide protein engineering and the hybrid bio/abio catalysts design for plastic upcycling without generating secondary environmental contamination.…”

Section: Main Textmentioning

confidence: 99%

“…The programmable degradation overcomes their incompatibility with industrial compost operations, making them viable polyolefin substitutes. [28][29][30] Analysis on the effects of polymer conformation and segmental cooperativity guide the thermal treatment of the polyester to spatially and temporally program degradation, while maintaining latency during processing and storage. The protectants are designed to regulate biocatalysis and stabilize enzymes during common plastic processing.…”

Section: Main Textmentioning

confidence: 99%

“…34 However, they are indifferentiable in landfills. 14 Typical residence times are not adequate to allow for full breakdown even in thermophilic digesters operating at 48-60 °C, 28,29 resulting in operational challenges and a financial burden to minimize contamination in organic waste. 30 Burkholderia cepacia lipase (BC-lipase) and Candida Antarctica lipase (CA-lipase) were embedded in PCL and proteinase K was embedded in PLA given their known hydrolysis ability in solution.…”

Section: Main Textmentioning

confidence: 99%

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Near-complete depolymerization of polyesters with nano-dispersed enzymes

DelRe

Jiang

Kang

et al. 2021

Nature

185

136

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Successfully interfacing enzymes and biomachineries with polymers affords ondemand modification and/or programmable plastic degradation during manufacture, utilization, and disposal, but requires controlled biocatalysis in solid matrices with macromolecular substrates. [1][2][3][4][5][6][7] Embedded enzyme microparticles have sped up polyester degradation, but compromise host properties and unintentionally accelerate microplastics formation with partial polymer degradation. 6,8,9 Here, by nanoscopically dispersing enzymes with deep active sites, semi-crystalline polyesters can be degraded primarily via chain-end mediated processive depolymerization with programmable latency and material integrity, akin to polyadenylationinduced mRNA decay. 10 It is also feasible to realize the processivity with enzymes having surface-exposed active sites by engineering enzyme/protectant/polymer complexes.Polycaprolactone and poly(lactic acid) containing less than 2 wt.% enzymes are depolymerized in days with up to 98% polymer-to-small molecule conversion in standard soil composts or household tap water, completely eliminating current needs to separate and landfill their products in compost facilities. Furthermore, oxidases embedded in polyolefins retain activities. However, the hydrocarbon polymers do not closely associate with enzymes like their polyester counterparts and the reactive radicals generated cannot chemically modify the macromolecular host. The studies described here provide molecular guidance toward the enzyme/polymer pairing and enzyme protectants' selection to modulate substrate selectivity and optimize biocatalytic pathways. They also highlight the need for in-depth research in solid-state enzymology, especially in multi-step enzymatic cascades, to tackle chemically dormant substrates without creating secondary environmental contamination and/or biosafety concerns.

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Section: Main Textmentioning

confidence: 99%

Section: Main Textmentioning

confidence: 99%

Section: Main Textmentioning

confidence: 99%

See 1 more Smart Citation

Near-complete depolymerization of polyesters with nano-dispersed enzymes

DelRe

Jiang

Kang

et al. 2021

Nature

185

136

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“…The CH 4 can then be captured and burned, which produces CO 2 and H 2 O, and the heat and energy can be recovered for use. This process yields a net-zero carbon balance for the bioplastic waste while also producing energy 229 , 230 . The efficiency of anaerobic digestion can be increased by including elements such as a ‘bioreactor landfill’, in which H 2 O is circulated to enhance microbial activities for CH 4 production 227 .…”

Section: End-of-life Treatment Scenariosmentioning

confidence: 99%

Bioplastics for a circular economy

2022

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Bioplastics — typically plastics manufactured from bio-based polymers — stand to contribute to more sustainable commercial plastic life cycles as part of a circular economy, in which virgin polymers are made from renewable or recycled raw materials. Carbon-neutral energy is used for production and products are reused or recycled at their end of life (EOL). In this Review, we assess the advantages and challenges of bioplastics in transitioning towards a circular economy. Compared with fossil-based plastics, bio-based plastics can have a lower carbon footprint and exhibit advantageous materials properties; moreover, they can be compatible with existing recycling streams and some offer biodegradation as an EOL scenario if performed in controlled or predictable environments. However, these benefits can have trade-offs, including negative agricultural impacts, competition with food production, unclear EOL management and higher costs. Emerging chemical and biological methods can enable the ‘upcycling’ of increasing volumes of heterogeneous plastic and bioplastic waste into higher-quality materials. To guide converters and consumers in their purchasing choices, existing (bio)plastic identification standards and life cycle assessment guidelines need revision and homogenization. Furthermore, clear regulation and financial incentives remain essential to scale from niche polymers to large-scale bioplastic market applications with truly sustainable impact.

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“…Commercial or household FW used as co-substrate in co-digestion studies includes FW from university canteens or catering [41,[45][46][47][48], food markets [46,49], artificial household FW [50,51], OFMSW [13,21,52] and industrial food processing waste [53]. However, FW can be a challenging co-substrate to study, due to its high nitrogen content and its high heterogeneity [54], especially for municipal and household FW.…”

Section: Co-digestion Substratesmentioning

confidence: 99%

Two Birds with One Stone: Bioplastics and Food Waste Anaerobic Co-Digestion

2022

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Following the BBC’s Blue Planet II nature documentary series on marine ecosystems, plastic packaging has come under public fire, with consumers demanding greener alternatives. The biodegradable properties of some bioplastics have offered a potential solution to the global challenge of plastic pollution, while enabling the capture of food waste through anaerobic digestion as a circular and energy-positive waste treatment strategy. However, despite their increasing popularity, currently bioplastics are being tested in environments that do not reflect real-life waste management scenarios. Bioplastics find their most useful, meaningful and environmentally-sound application in food packaging—why is there so little interest in addressing their anaerobic co-digestion with food waste? Here, we provide a set of recommendations to ensure future studies on bioplastic end-of-life are fit for purpose. This perspective makes the link between the environmental sustainability of bioplastics and the role of food waste anaerobic digestion as we move towards an integrated food–energy–water–waste nexus. It shines light on a novel outlook in the field of bioplastic waste management while uncovering the complexity of a successful path forward. Ultimately, this research strives to ensure that the promotion of bioplastics within a circular economy framework is supported across waste collection and treatment stages.

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Anaerobic Codigestion of Food Waste and Polylactic Acid: Effect of Pretreatment on Methane Yield and Solid Reduction

Cited by 45 publications

References 31 publications

Near-complete depolymerization of polyesters with nano-dispersed enzymes

Near-complete depolymerization of polyesters with nano-dispersed enzymes

Bioplastics for a circular economy

Two Birds with One Stone: Bioplastics and Food Waste Anaerobic Co-Digestion

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