Assessing potential of biochar for increasing water-holding capacity of sandy soils

Increasing the water-holding capacity of sandy soils will help improve efficiency of water use in agricultural production, and may be critical for providing enough energy and food for an increasing global population. We hypothesized that addition of biochar will increase the water-holding capacity of a sandy loam soil, and that the depth of biochar incorporation will influence the rate of biochar surface oxidation in the amended soils. Hardwood fast pyrolysis biochar was mixed with soil (0%, 3%, and 6% w/w) and placed into columns in either the bottom 11.4 cm or the top 11.4 cm to simulate deep banding in rows (DBR) and uniform topsoil mixing (UTM) applications, respectively. Four sets of 18 columns were incubated at 30 °C and 80% RH. Every 7 days, 150 mL of 0.001 M calcium chloride solution was added to the columns to produce leaching. Sets of columns were harvested after 1, 15, 29, and 91 days. Addition of biochar increased the gravity-drained water content 23% relative to the control. Bulk density of the control soils increased with incubation time (from 1.41 to 1.45 g cm−3), whereas bulk density of biochar-treated soils was up to 9% less than the control and remained constant throughout the incubation period. Biochar did not affect the CEC of the soil. The results suggest that biochar added to sandy loam soil increases water-holding capacity and might increase water available for crop use

Co-combustion of sewage sludge from different treatment processes and a lignite coal in a laboratory scale combustor

One sustainable use of sewage sludge (SS) is to use it as fuel in existing coal-fired plants. Towards this end, this study evaluated thermal characteristics and co-combustion efficiency of dried SS samples from six wastewater treatment plants with different sludge treatment units. Fuel quality of SS based on proximate and ultimate analyses and calorific value, and ash composition by XRF analysis were investigated. Then the SS samples were co-combusted in a laboratory batch reactor in mixtures with coal (3%, 5%, 10%, 20% and 30%). Results showed that samples had good calorific values (between 1931 and 3852 cal/g). Furthermore, the type of sludge stabilization processes had an important effect on thermal characteristics of samples and the point where the sludge addition started to intrude the combustion efficiency. Among all stabilization methods, lime stabilization was observed to affect the thermal characteristics the most. Sludge treated with anaerobic stabilization had lower calorific values than the ones stabilized aerobically. The results from co-combustion experiments showed that as the percentage of SS in the mixture increased from 5% to 30%, the combustion efficiency decreased gradually from 99.5% to 973%. Furthermore, according to XRF analysis result, fouling and slagging indices of samples were higher than the limit values