Whiskey distillery waste streams consisting of pot ale (liquid residue) and spent grain (solid residue) are high strength organic wastes and suitable feedstock for anaerobic digestion (AD) from both economic and environmental stand points. Anaerobic digestion of pot ale and pot ale/spent grain mixtures (with mixing ratios of 1:1, 1:3, and 1:5 by wet weight) was performed after implementation of a novel hybrid pre-treatment (combined chemical and mechanical) in order to modify lignocellulosic structure and ultimately enhance digestion yield. Lignin, hemicellulose, and cellulose fractions were determined before and after chemical pre-treatment. Effects of different inoculum rates (10–30–50% on wet basis) and beating times (0–7.5–15 min) on anaerobic digestion of pot ale alone and of pot ale/spent grain mixtures were investigated in lab scale batch mode with a major focus of optimising biogas yield by using response surface methodology (RSM) in Design Expert Software. The highest biogas yields of 629 ± 8.5 mL/g vs. (51.3% CH₄) and 360 ± 10 mL/g vs. (55.0 ± 0.4) with anaerobic digestion of pot ale alone and spent grain mix after 1M NaOH and 7.5 min beating pre-treatments with 50% inoculum ratio respectively. The optimum digestion conditions to maximise the biogas quality and quantity were predicted as 10 and 13 min beating times and 32 and 38 °C digestion temperatures for anaerobic digestion of pot ale alone and spent grain mix respectively.

Cassava is a form of food that is rich in starch abundant in many countries. Several bio-products can be extracted from its starch and used as an alternative for oil-based products. This study primarily aims to investigate the influence of the starch isolated from cassava peel on the quantity and quality of the biogas produced via anaerobic digestion. Beating pre-treatment was applied for the first time to isolate the starch and mechanically pre-treat the substrate. The influence of temperature, volatile solid and sludge quantity investigations were analysed with the aid of Design of Experiments (DOE). An optimisation process was applied in calculating the energy balance at the optimal results and this was needed in evaluating the impact of the starch on the biogas produced. The study revealed that the influence of the starch on the biogas quality is quite low and, as such, negligible. The largest biogas volume as obtained was 3830 cc at 37 °C, 4.2 g-VS and 50% sludge quantity, while at the same time the maximum CH₄ g⁻¹-VS was 850 cc g⁻¹-VS at 37 °C, 1.1 g-VS and 50% sludge quantity. The optimal results show the energy gain could be achieved based on the set criteria.

Anaerobic digestion (AD) has undergone many developments since its first appearance. Despite that, there are still some environmental and economical obstacles that are limiting its sustainability. On the other hand, different types of starch have proven their effectiveness in some different applications. Food processing industries are considered one of the largest generators of waste in the environment. With an aid of the response surface methodology (RSM), the proposed study aimed to find an optimised way to overcome the obstacles by studying the impacts of the starch isolated from the potato peels on the biogas produced from the AD of potato peels before and after starch separation. The study found that potato peels represented approximately 12.5% of the potato total weight. The starch has only a slight influence on the quantity of the biogas produced and much lower influences on its quality. This finding suggests further investigation is required on the production of starch bio-based products simultaneously with the biogas and bio-slurry, which may mitigate environmental influences and economical obstacles of AD and make it more commercially attractive. The study showed also that the highest energy gain by the g-VS/0.2 L of potato peels was 62.9% at 35 °C, 1.62 g-VS/0.2 L organic concentration and 50% sludge concentration, which yielded a maximum CH₄ of 72.4%.

Dates are an important food source in many countries that produce different types of dates. Dates have a significant amount of waste, either from planting or eating them. A large amount of seeds are produced from eating it. This study is considered to explore the quantity and the quality of biogas produced from the Sagai date seeds through the anaerobic digestion process (AD) before and after oil extraction and exploitation of oil in biodiesel production. In addition, the study aims to tests the resulted digestate from the AD process. This test was performed to ensure that the digestate contains the three basics elements (N, P and K) to be used in agriculture. In its preparation, the date seeds were ground after washing via a grinding machine without exposure to any other treatment process. Design of Experiments (DOE) was applied in determining the effect of temperature, volatile solid and sludge quantity on the resulted biogas. The energy balance at the optimum results was calculated. The highest biogas volumes from the AD of date seed before and after oil extraction were 4140 cc and 3534 cc, respectively, at 37 °C, 4.2 g-VS and 50% sludge quantity. While the highest methane/g-VS were 1143.8 cc/g-VS and 949.6 cc/g-VS, respectively, at 37 °C, 1.1 g-VS and 50% sludge quantity. The oil obtained using the Soxhlet method at 70 °C, 1:4 ratio of date seeds to n-hexane solvent and 5 h reaction time was 16% of the date seed mass (79% biodiesel and 9% glycerine). Therefore, the resultant effect from the main findings indicated that the study supports the investigation of the possibility of exploiting date seeds in the production of biogas, biodiesel and bio-fertiliser.