Cellulose Fiber/Bentonite Clay/Biodegradable Thermoplastic Composites

Adding cellulose fiber reinforcement can improve mechanical properties of biodegradable plastics, but fiber must be well dispersed to achieve any benefit. The approach to dispersing fiber in this study was to use aqueous gels of sodium bentonite clay. These clay-fiber gels were combined with powdered compostable thermoplastics and calcium carbonate filler. The composite was dried, twin-screw extruded, and injection molded to make thin parts for tensile testing. An experimental design was used to determine the effect of fiber concentration, fiber length, and clay concentration. Polybutylene adipate/terephthalate copolymer (PBAT) and 70/30 polylactic acid (PLA)/PBAT blend were the biodegradable plastics studied. The composite strength decreased compared to the thermoplastics (13 vs. 19 MPa for PBAT, 27 vs. 38 MPa for the PLA/PBAT blend). The composite elongation to break decreased compared to the thermoplastics (170% vs. 831% for PBAT, 4.9% vs. 8.7% for the PLA/PBAT blend). The modulus increased for the composites compared to the thermoplastic standards (149 vs. 61 MPa for PBAT, 1328 vs. 965 MPa for the PLA/PBAT blend). All composite samples had good water resistance.     

Report: anaerobic digestion of a sulphate-rich high-strength landfill leachate: the effect of differential dosing with FeCl3.

The effect of different dose concentrations of FeCl3 on the performance of a mesophilic anaerobic digester treating a highly alkaline, high-strength and sulphate-rich landfill leachate was tested. The results indicated that sulphate reduction was the predominant reaction and methanogenic processes were entirely inhibited in the reactor without FeCl3 addition. Adding FeCl3 into the reactor restored some methanogenic activity and also improved the rates of sulphate reduction. A combination of sulphate reduction and methanogenic activity resulted in up to 75% chemical oxygen demand (COD) removal and 85% sulphate removal. Sulphate reduction remained the principle mechanism by which COD removal took place with a methane yield of only between 0.14 and 0.18 m3 CH4 kg(-1) COD removed being achieved. The process was, however, stable and offered advantages for the further treatment or conveyance of the anaerobically treated leachate.     

Ecological Benefits of the Conservation Reserve Program

The Conservation Reserve Program was initiated in 1985 to reduce soil loss on highly erodible agricultural land. This stated objective of the program has been quite successful. However, there are other unintentional yet significant ecological benefits to the program that merit evaluation. These benefits include the reversal of landscape fragmentation, maintenance of regional biodiversity, creation of wildlife habitat, and favorable changes in regional carbon flux. These and other benefits should be used by policy makers and federal officials to maintain the program even after enrollment expectations have been achieved.