Adsorption of acid-extractable organics from oil sands process-affected water onto biomass-based biochar: Metal content matters

The impact of biochar properties on acid-extractable organics (AEO) adsorption from oil sands process-affected water (OSPW) was studied. Biochar from wheat straw with the highest ash content (14%) had the highest adsorption capacity (0.59 mg/g) followed by biochar from pulp mill sludge, switchgrass, mountain pine, hemp shives, and aspen wood. The adsorption capacity had no obvious trend with surface area, total pore volume, bulk polarity and aromaticity. The large impact of metal content was consistent with the carboxylates (i.e., naphthenate species) in the OSPW binding to the metals (mainly Al and Fe) on the carbon substrate. Although the capacity of biochar is still approximately two orders of magnitude lower than that of a commercial activated carbon, confirming the property (i.e., metal content) that most influenced AEO adsorption, may allow biochar to become competitive with activated carbon after normalizing for cost, especially if this cost includes environmental impacts.

Mapping thermomechanical pulp sludge (TMPS) biochar characteristics for greenhouse produce safety

This study evaluates the existence of toxic compounds in thermomechanical pulp sludge (TMPS) derived biochars obtained through a slow pyrolysis process and establishes the criteria for manufacturing benign-quality biochar for safe greenhouse-based food production. Accordingly, nine TMPS biochars generated at different temperatures (450, 500, 550 °C) and residence times (30, 60, 120 min) were investigated. Depending on the production conditions, the polycyclic aromatic hydrocarbons (PAHs) sum varied from 0.4 to 236 μg/g biochar. Interestingly, correlations between the PAH content, toxicity, and process conditions were derived in the form of process toxicity relationships (PTRs). On the basis of the learning garnered in this study, it is recommended that TMPS feedstock will yield benign quality biochar when processed at a minimum 500 °C temperature for an optimum residence time of 30 min.

Interconnected carbon nanosheets derived from hemp for ultrafast supercapacitors with high energy

We created unique interconnected partially graphitic carbon nanosheets (10-30 nm in thickness) with high specific surface area (up to 2287 m(2) g(-1)), significant volume fraction of mesoporosity (up to 58%), and good electrical conductivity (211-226 S m(-1)) from hemp bast fiber. The nanosheets are ideally suited for low (down to 0 °C) through high (100 °C) temperature ionic-liquid-based supercapacitor applications: At 0 °C and a current density of 10 A g(-1), the electrode maintains a remarkable capacitance of 106 F g(-1). At 20, 60, and 100 °C and an extreme current density of 100 A g(-1), there is excellent capacitance retention (72-92%) with the specific capacitances being 113, 144, and 142 F g(-1), respectively. These characteristics favorably place the materials on a Ragone chart providing among the best power-energy characteristics (on an active mass normalized basis) ever reported for an electrochemical capacitor: At a very high power density of 20 kW kg(-1) and 20, 60, and 100 °C, the energy densities are 19, 34, and 40 Wh kg(-1), respectively. Moreover the assembled supercapacitor device yields a maximum energy density of 12 Wh kg(-1), which is higher than that of commercially available supercapacitors. By taking advantage of the complex multilayered structure of a hemp bast fiber precursor, such exquisite carbons were able to be achieved by simple hydrothermal carbonization combined with activation. This novel precursor-synthesis route presents a great potential for facile large-scale production of high-performance carbons for a variety of diverse applications including energy storage.

Development of agri-pellet production cost and optimum size

Minimum production cost and optimum plant size were determined for pellet plants using agricultural biomass residue from wheat, barley and oats. Three scenarios involving minimum, average and maximum yields of straw were considered for developing a techno-economic model. The life cycle cost of producing pellets in Western Canada was estimated. The economically optimum size of production plant for the three yield scenarios in tonne year(-1) were 70,000, 150,000 and 150,000, respectively. The corresponding costs of production per tonne are $170.89, $129.42 and $122.17, respectively. However, the cost of pellets does not change much for capacities over 70,000 tonne year(-1) for both the average and maximum yields. The optimum size is same for both average and maximum yield cases. Sensitivity analyses have showed that the total cost of pellet production is most sensitive to field cost followed by transportation cost. Currently, the cost of energy from agri-pellets is higher than that of energy from natural gas.