Limitation of direct current (DC) injection into the alternating current (AC) network is an important operational requirement for grid-connected photovoltaic (PV) systems. One way to ensure that this requirement is met is to use a power transformer as interface to the AC network. But this adds costs, mass, volume and power losses. In a transformerless system, the inverter forming part of the PV system has to be operated so that the DC content in its output current is below the specified limits. Ideally, there should be no DC at the output of the inverter, but in practice, in the absence of special measures, a small amount of DC current is present. A technique for elimination of the DC-offset is proposed. It is based on the sensing of the DC-offset voltage at the output of the inverter. A sensor output is used to drive a feedback system designed to control the operation of the inverter so that the DC-offset is forced to stay within the acceptable limits. A mathematical model for the DC-offset controller is derived. A design procedure, based on the model, is proposed for the controller. The results of tests performed on a system of 1 kW nominal rating provide validation for the mathematical model.

This research investigates ethanol production from waste lignocellulosic material (sugarcane bagasse). The bagasse was first pretreated using chemicals and ultrasound techniques. These pretreatment techniques were applied separately and combined. The pretreated bagasse was then fermented anaerobically for biofuel production without enzymatic hydrolysis. The results showed higher ethanol production than those reported in the literature. The maximum ethanol production of 820 mg/L was achieved with a combination of ultrasound (60 amplitude level, 127 W) and acid (3% H₂SO₄ concentration). The combination of two-step pretreatment such as an ultrasound (50 amplitude level, 109 W) with acid (3% H₂SO₄ concentration) and then an ultrasound with alkaline (23% NaOH concentration) generated 911 mg/L of ethanol.

Globally, the most problematic greenhouse gas (GHG) emissions of ruminant livestock is methane (CH₄), with a global warming potential 25 times that of carbon dioxide. This work considers the emissions and production effects of powdered activated carbon (PAC) at 0.5% by dry matter (DM) on methanogenic rumen flora as the major source of dairy cattle enteric methane emissions. In total, 180 dairy cattle located in Brymaroo, Queensland (QLD), Australia, were studied in a three-cycle repeated measures ANOVA format with a 4 week primary interval. Emissions eructated during milking and in faecal deposits were measured, and in addition, 16S rRNA gene sequencing was performed to determine the collective populations of prokaryotic bacteria and archaea as well methanogenic communities for each treatment. Moreover, 0.5% PAC addition reduced CH₄ emissions by 30–40% and CO₂ emissions by 10%, while improving daily milk production by 3.43%, milk protein by 2.63% and milk fat by 6.32%, on average for the herd (p < 0.001 in all cases). rRNA gene sequencing showed populations of methanogenic flora decreased by 30% on average with a corresponding increase in the nonmethanogenic species. We strongly advocate further on-farm trials with the dietary addition of PAC in ruminant diets to mitigate emissions while maintaining or improving productivity.

Agricultural runoff is a major cause of degradation to freshwater sources. Nitrate is of particular interest, due to the abundant use of nitrogen-based fertilizers in agricultural practices globally. This study investigated the nitrate removal of biochar produced from an agricultural waste product, macadamia nutshell (MBC). Kinetic experiments and structural analyses showed that MBC pyrolsed at 900 °C exhibited inferior NO₃⁻ removal compared to that pyrolsed at 1000 °C, which was subsequently used in the column experiments. Concentrations of 5, 10 and 15 mg/L, with flowrates of 2, 5 and 10 mL/min, were examined over a 360 min treatment time. Detailed statistical analyses were applied using 2³ factorial design. Nitrate removal was significantly affected by flowrate, concentration and their interactions. The highest nitrate removal capacity of 0.11 mg/g MBC was achieved at a NO₃⁻ concentration of 15 mg/L and flowrate of 2 mL/min. The more crystalline structure and rough texture of MBC prepared at 1000 °C resulted in higher NO₃⁻ removal compared to MBC prepared at 900 °C. The operating parameters with the highest NO₃⁻ removal were used to study the removal capacity of the column. Breakthrough and exhaustion times of the column were 25 and 330 min respectively. Approximately 92% of the column bed was saturated after exhaustion.