Straw, biodegradation

Products of Wheat Straw Biodegradation by Cyathus stercoreus... 

Clockwise from top left) Biodegradable mulches An ornamental bark mulch, good around shrubs and at the base of hedges lawn clippings used as a mulch in the vegetable plot, here spread over layers of newspaper (see also overleaf)] one-year-old leaf mold well-rotted straw. 

Figure 4. Biodegradation of HCl/dioxane-isolated C-labeled straw lignin by 50 mL washed P. chrysosporium mycelial pellets ( ) in the presence of 2.5 units glucose oxidase accelerative effect engendered by 2 units lignin peroxidase in absence (Q) and presence (H) of 75 /imole veratryl alcohol. Adapted and redrawn from reference 34.

It should be pointed out that the raw materials for VAM and its related polymers (i.e. ethylene and acetic acid) are produced from fossil resources, mainly crude oil. It is possible to completely substitute the feedstock for these raw materials and switch to ethanol, which can be produced from renewable resources like sugar cane, com, or preferably straw and other non-food parts of plants. Having that in mind, the whole production of PVAc, that nowadays is based on traditional fossil resources, could be switched to a renewable, sustainable and C02-neutral production process based on bioethanol, as shown in Fig. 3. If the vinyl acetate circle can be closed by the important steps of biodegradation or hydrolysis and biodegradation of vinyl ester-based polymers back to carbon dioxide, then a tmly sustainable material circle can be established. 

For example, when cell walls of maize stem were treated with sodium hydroxide (0.1M) at 20°C for various times to release different amounts of phenolics, a highly significant correlation (r = 0.98) was found between the amount of phenolics released and wall biodegradability (measured by cellulase ) (5). It is of interest to note that alkali treatment of poor quality graminaceous forages (e.g., cereal straw) is used commercially to increase their biodegradability, and thus their feed value for the animal (1). 

Historically, pricing had been the biggest barrier to biodegradable polymer market development. However, growing volumes of production and the development of new technology should further allow bio-based resin makers to reduce costs. Using materials such as corn stover, wheat straw and rice straw, which remain in fields after crops are harvested, as resin feedstock, could also increase productivity and economic performance. 

AgroResin is a biodegradable packaging material from by-products of the palm oil industry. It can also be made from agricultural fibres, such as wheat straw. It is compatible with existing moulded pulp manufacturing processes. AgroResin has received Din-Certco certification for products made of compostable materials (DIN EN 13432 2000-12). 

Sunway offers disposable tableware made of biodegradable materials. The product range includes cups, plates, dishes, cutlery, drinking straws and decorations. 

Cheng et al. (2008) deduced that the degradation kinetics of DEHP in thermophihc phase and the phase thereafter were modeled by first-order and fractional power kinetics, respectively. Recently, Chang et al. (2009) investigated the biodegradation of PAEs, DBP, and DEHP in compost and compost-amended soil. Both DBP and DEHP were added to straw and animal manure composts at a concentration of 50 mg kg and subsequently added to the soil. Chang et al. (2009) noted that the addition of either compost individually improved the rate of PAE degradation in the compost-amended soil. 

Disposal. An estimated 2.3 billion barrels of crude oil were produced in 1997 (API 1998a). From this crude oil, TPH waste may be generated in a number of ways that ultimately lead to either improper or acceptable disposal. Incineration is a primary method of disposal for wastes containing TPH. Oil spills are frequently captured and treated using various absorbents (e.g., straw, polyurethane foam, activated carbon, peat), gelling agents, dispersants, and mechanical systems. Biodegradation also has been used to treat contaminated soil (OHM/TADS 1985). 

Flaig (1966a) has reported elemental analysis for a humic acid formed from decaying straw (Table 7). Here, the prime source was ligniferous plant tissue. A humic acid of typical elemental composition was obtained from a ligniferous source. More recent evidence supports this type of biodegradation, based on direct NMR monitoring (Ellwardt et al., 1981). A number of soil humic acids fit these data. 

Land Farming. Land treatment is the most common method of oily solids disposal. The process is frequently referred to as land farming, as the oily waste is spread thinly, worked into the soil, fertilized, and watered. Manure or straw is added to reduce erosion lime addition reduces alkalinity. Commercially available strains of biodegrading bacteria may also be added to supplement the activity of naturally occurring strains. Because prevention of groundwater contamination is a serious concern, the same regulatory requirements applicable to landfill sites must be satisfied. 

Table III. GC-MS Identified TMS Derivatives of Biodegraded and Oxidized Wheat Straw ...

Biopolymers can be directly obtained [KOB 03] fiom hemicellulose in com or starch. Starch, a major polymer from arable crops, is a good candidate for the production of biodegradable packaging or objects. If combined with a compound of wheat straw, its potential apphcations could increase. 

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