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.
A significant expansion of anaerobic digestion (AD) processes would certainly result in a reduction in the current dependence on fossil fuels. The operational costs, the large amounts of digestate generated and the expenses of dealing with it and the volatility of the fuel indexes represent major environmental and economical challenges to the diffusion of AD. Increasing the bio-products of AD could possibly help in increasing its profitability and limit these challenges. This study investigates the influence of mango starch and seed coats on the biogas produced from mango waste. To overcome the environmental challenges, the digestate was tested and its bio-fertiliser potential proven. The study reached the conclusion that the effect of the starch on the AD biogas of mango waste is low while the effect of the seed coats is quite high. This finding supports further investigations to evaluate the effect of the production of mango starch and seed coat-based products on the profitability of AD. The highest energy balance achieved was 65% at 32 °C, 3.93 g-VS organic concentration and 37% sludge concentration, which yielded a maximum CH4 yield of 62.5%. This finding encourages the application of gate fees for accepting bio-waste, which may help in overcoming its economic challenges.
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%.
The rapid increase in the world population has caused an enormous increase in the demand of energy. Growing demand has resulted in a shortfall in conventional energy resources. Due to that and because of the major negative impacts of fossil fuel on the environment and other aspects as well, the necessity toward finding alternative cheap, renewable, and environmentally friendly energy resources has significantly arose. Biomass as an energy resource has a potential to be a good alternative for non-renewable energy resources. Anaerobic digestion process is one of the most commonly biological conversion process used in converting biomass into biofuels. It has been extensively applied in many studies for converting several types of feedstocks and has proved its significant effectiveness. (AD) digestates are generally composed of solid and liquid streams. Those streams are rich in nutrients and contain undigested materials which have not been digested in the digestion process. Despite the significant effectiveness, it would contribute in major issues if it has been applied at large scale, as the amount of digestates which would be generated is quite high. Due to that and to take an advantage of the digestates in the production of biofuel and bioproducts as well, the interests in enhancing and utilizing anaerobic digestion residues have recently much increased. Bioethanol is one of the most promising liquid biofuel. It is eco-friendly alternative to fossil fuels. In recent years, number of studies have investigated the integration approach of producing biogas and bioproduct in which would result in zero waste. However, this paper discusses mainly an integration approach for producing two promising renewable energies can be utilized in many applications with no waste generated. This approach is still at an early stage and requires further studies to improve the properties of the biofuels and high-value bio-based products produced.
The transformation to renewable energy has become a requirement nowadays. Thermoplastic starch (TPS) is a type of bio-plastic. Its quality and properties are examined by employing mechanical, physical, and other tests. Despite the proven advantages of using anaerobic digestion (AD) for the conversion of biomass into biogas and the developments on it, there still exist some environmental and economical challenges limiting prosperity and sustainability of AD. Economically, compared to fossil fuel market, biogas, which is the only major product of AD, is not competitive enough compared to the prices of its counterparts.
With the aid of Design Expert software, the present study mainly aims to design and implement an integrated approach so as to potentially overcome these challenges and to make the AD more desirable. The approach incorporates the AD process with the process of producing TPS to form; biogas, bio-slurry and TPS/mango fibre bio-plastic sheet, from the residues of three starchy biomass: potato, mango and avocado. A Hollander Beater was employed as a multi-functional device, to: pre-treat the biomass, isolate the starch and to process mango seed coats. The study found that, the highest energy gain per gram of volatile solids of potato residues was 62.9% at 35 ⁰C, 1.62 g-VS organic concentration and 50% sludge concentration, which yielded a maximum CH4% of 72.4%. While, the highest energy gain by the gram of volatile solids of mango and avocado residues were 65% and 16.5% which yielded a maximum CH4% of 62.4% and 60.9% respectively. The production of a bioplastic sheet with a dimension of 2440*1220*3.2 mm has the same specifications of the optimal bio-plastic sheet produced, resulting in a cost efficiency of up to 65%. To achieve this approximately 353.7 kg potato, 89.9 kg mango and 173.7 kg avocado requires processing.
Therefore the proposed study has achieved its main aim. Economically, this was achieved as a result of an excess amount of the bio-energy been produced (approximately 29%) of the total bio-energy produced. Regarding the environmental challenges which mainly depend on the accumulation of large amounts of the generated digestate, the study has confirmed the biofertiliser potential of the digestate with a suggestion to carry out more tests to confirm its quality and increase the reliability. Countries such as Saudi Arabia which is emerging in this field, can greatly benefit from this study via identifying the obstacles, tackling and avoiding them to improve profitability.
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