A new method for detecting micro-fragments of biodegradable mulch films containing poly(butylene adipate-co-terephthalate) (PBAT) in soil.

Biodegradable mulch (BDM) is a potentially sustainable alternative to polyethylene plastic mulch film for intensive crop production. Certified BDMs must demonstrate >90% biodegradation in compost and agricultural soil, but the environmental fate of BDM micro-fragments is usually not measured. While using fatty acid methyl ester (FAME) analysis to study changes in soil microbial communities under different BDMs and management conditions, two peaks were detected by gas chromatography that were derived from a BDM containing poly(butylene adipate-co-terephthalate) (PBAT). The largest peak was identified as 1,4-benzenedicarboxylic acid, dimethyl ester, or dimethyl terephthalate (DMT). The smaller peak was hexanedioic acid dimethyl ester or dimethyl adipate. From this observation we hypothesized that the FAME method could be used to detect and quantify micro-fragments (<5 mm in length) of PBAT-containing BDM in soil. To test this, fragments of two commercially available BDMs were added to soil and extracted for FAME analyses. Linear relationships were observed between DMT and mulch mass added to soil for both BDMs when the initial mass of fragments was <3.5 mg (r2   > .99). Based on our findings, the FAME method could be redeployed to study the environmental fate and possible accumulation of BDM micro-fragments in soil over time.

Biocomposites of Low-Density Polyethylene Plus Wood Flour or Flax Straw: Biodegradation Kinetics across Three Environments.

The purpose of this study was to assess the potential for biocomposite films to biodegrade in diverse climatic environments. Biocomposite films based on polyethylene and 30 wt.% of two lignocellulosic fillers (wood flour or flax straw) of different size fractions were prepared and studied. The developed composite films were characterized by satisfactory mechanical properties that allows the use of these materials for various applications. The biodegradability was evaluated in soil across three environments: laboratory conditions, an open field in Russia, and an open field in Costa Rica. All the samples lost weight and tensile strength during biodegradation tests, which was associated with the physicochemical degradation of both the natural filler and the polymer matrix. The spectral density of the band at 1463 cm-1 related to CH2-groups in polyethylene chains decreased in the process of soil burial, which is evidence of polymer chain breakage with formation of CH3 end groups. The degradation rate of most biocomposites after 20 months of the soil assays was greatest in Costa Rica (20.8-30.9%), followed by laboratory conditions (16.0-23.3%), and lowest in Russia (13.2-22.0%). The biocomposites with flax straw were more prone to biodegradation than those with wood flour, which can be explained by the chemical composition of fillers and the shape of filler particles. As the size fraction of filler particles increased, the biodegradation rate increased. Large particles had higher bioavailability than small spherical ones, encapsulated by a polymer. The prepared biocomposites have potential as an ecofriendly replacement for traditional polyolefins, especially in warmer climates.

Environmental challenges threatening the growth of urban agriculture in the United States.

Urban agriculture, though often difficult to define, is an emerging sector of local food economies in the United States. Although urban and agricultural landscapes are often integrated in countries around the world, the establishment of mid- to large-scale food production in the U.S. urban ecosystem is a relatively new development. Many of the urban agricultural projects in the United States have emerged from social movements and nonprofit organizations focused on urban renewal, education, job training, community development, and sustainability initiatives. Although these social initiatives have traction, critical knowledge gaps exist regarding the science of food production in urban ecosystems. Developing a science-based approach to urban agriculture is essential to the economic and environmental sustainability of the movement. This paper reviews abiotic environmental factors influencing urban cropping systems, including soil contamination and remediation; atmospheric pollutants and altered climatic conditions; and water management, sources, and safety. This review paper seeks to characterize the limited state of the science on urban agricultural systems and identify future research questions most relevant to urban farmers, land-use planners, and environmental consultants.