EFFECT OF SEEDING OF WOOD-ASH ON BIOGAS PRODUCTION USING PIG WASTE AND CASSAVA PEELS

EFFECT OF SEEDING OF WOOD-ASH ON BIOGAS PRODUCTION USING PIG WASTE AND CASSAVA PEELS

ABSTRACT

The rapid expansion of cassava-based agroindustries in Nigeria has resulted in a massive increase in the amount of garbage consisting of cassava peels, as of 13 July 2019. An investigation was conducted to determine whether or not it would be possible to produce biogas and biofertilizer from discarded cassava peels and pig manure for use in both agricultural and home settings. Cassava peels, both fresh and stale, were utilised in the research. Cassava peels and pig waste slurry were both pretreated with three different pretreatment chemicals, including sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)2, and ammonium chloride (NH4Cl) buffer solutions. For the purpose of this investigation, six batch anaerobic biodigesters, each with a capacity of 10 litres, were utilised for a retention duration of 40 days. The pH, temperature, and quantities of biogas and methane produced by the cassava peels were recorded and monitored daily, as was the production of methane. The official methods of analysis developed by the Association of Official Analytical Chemists (AOAC) were utilised in order to ascertain the fertiliser characteristics (total solids, volatile solids, percentage of phosphorus, percentage of biogas biofertilizer nitrogen, etc.) of the digester slurry and the digester sludge following 40 days of anaerobic digestion. The findings indicated that the amount of biogas produced each day is 2540 cm3 of volume. The use of stale cassava peels and pig waste slurry in conjunction with the application of the NH4Cl pretreatment chemical resulted in the highest levels of biogas generation and methane output, which were respectively 104,961 cm3 and 62.3%. The sludge that was produced in the digester as a result of the anaerobic digestion of cassava peels and pig dung was shown to have beneficial properties as a biofertilizer.

1.0 INTRODUCTION
Because of rising population levels, more urbanisation, and expanded industrialization across the globe, there has been a significant and concerning rise in the amount of energy that is required. This issue is particularly pronounced in nations that are still considered to be developing or undeveloped since the social and economic situations there are relatively poor. Lack of infrastructures for energy generation, transmission, and distribution, unavailability of nonrenewable energy sources such as fossil fuels, low technology for energy conversion from renewable energy sources such as biogas, and lack of funds for purchase of fossil fuels, infrastructural and technology developments in energy sectors have all been implicated in the near energy crisis in most underdeveloped and developing countries (Aisien, et. al., 2010; Kwasi – Effah et al). However, because energy can be obtained from renewable energy sources such as waste materials, the issue of poverty in underdeveloped and emerging nations can be significantly decreased. This is because the energy crisis is caused by a lack of renewable energy sources. The renewable energy source, such as biogas production from anaerobic digestion of organic waste materials, which may be generated from municipal solid waste, agricultural waste, industrial waste, and home waste, can offer large amounts of energy all over the world (Aisien et. al., 2007b; Igbum, et. al., 2019). [Citation needed] (Aisien et. al., 2007b; Igbum, et. al. In addition to that, biogas can be manufactured from discarded food (Huiru et al., 2019). Biogas is an affordable kind of renewable energy that has the potential to fulfil the energy requirements of the world’s rural population to a significant extent. It is a combustible gas that is odourless and created by the anaerobic digestion of organic waste products. According to Buren (1979), this fuel does not produce smoke, it is hygienic, and it is more convenient to use than other solid fuels. Not only will an increased emphasis on the use of renewable energy from biogas rather than the nonrenewable energy source of fossil fuels reduce energy demands from fossil fuels, which are becoming very expensive and can lead to an energy crisis, but it will also address the problems of greenhouse gas emissions, global warming, environmental pollution/degradation, and health hazard (COP 21, 2015; Igbum, et al., 2019). This is important because fossil fuels are becoming increasingly expensive and The anaerobic biological decomposition of organic materials in the absence of oxygen results in the production of the renewable energy source known as biogas. According to Mel et al. (2015), the biogas that results from the anaerobic digestion of organic waste is a gas that contains methane (50-72 volume percent), carbon (IV) oxide (25-45 volume percent), nitrogen (>2 volume percent), hydrogen sulphide (>1 volume percent), water (2-7 volume percent) and oxygen (>2 volume percent). The generation of biogas is accomplished primarily through three distinct biochemical processes. As can be seen in the following table, these processes are known as hydrolysis, acidogenesis/acetogenesis, and methanogenesis (Igwe, 2014).
(C6H10O5)n + nH2O → n(C6H12O6) – Hydrolysis (1) n(C6H12O6) → nCH3COOH – Acetogenesis/Acidogenesis (2) 3nCH3COOH → nCH4 + CO2 – Methanogenesis (3)
The lighting, heating, and cooking, as well as the creation of power and fuel for vehicles, are all examples of successful use of biogas energy. According to Aisien et al. (2007), the sludge that is produced during the anaerobic digestion of waste materials has the potential to be utilised as a biofertilizer in order to increase the fertility of the soil.

According to the International Institute of Tropical Agriculture (IITA), Nigeria is the country that produces the most cassava (Manihot esculenta Crantz), with an annual output of over 46 million tonnes. According to FAO (2001), the processing of one tonne of fresh cassava root results in the production of around 250 to 300 kilogrammes of cassava peels. The peel of the cassava root makes up between 8 and 15 weight percent of the root’s total dry matter. The composition of cassava peels includes 20–31 weight percent of hemicelluloses, 16–42 weight percent of cellulose, and 6–8 weight percent of lignin. According to Kongkiattikajorn and Sornvorawea (2011), in addition to fibre, peels contain between 81.9 and 93.9 weight percent of organic matter and between 4.1 and 6.5 weight percent of crude protein. The analysis of the mineral composition of cassava peel revealed the following mineral content: 48.7 wt.% carbon, 1 wt.% nitrogen, 1.1 wt.% potassium, 1.6 wt.% phosphorus, 0.16 wt.% nitrogen dioxide, 0.15 wt.% sodium, 0.9 wt.% calcium, 125 mg/kg zinc, 15 mg/kg copper, 180 mg/kg manganese, 16.7 mg/kg lead, 48.
Garri, starch, fufu, lafu, and flour made from cassava have all seen significant increases in output as a direct result of the country of Nigeria’s rapidly growing population as well as its relatively inexpensive standard of living. Because of this, there has been a significant rise in the amount of waste consisting of cassava peels. Other waste products that result from the processing of cassava in Nigeria include cassava wastewater, sievates, and offal (waste products from the manufacturing of “foo-foo”). According to a report from the International Livestock Research Institute (ILRI) in 2015, roughly 98% of Nigeria’s cassava peels are wasted annually owing to the limits connected with drying. ILRI was concerned about the safe usage of cassava peels due to the presence of hydrocyanide and mycotoxins related to food poisoning. The careless disposal of cassava peels in landfills and other garbage dump sites has resulted in significant contamination of the surrounding environment. The breakdown of this waste results in the production of poisonous leachate, which pollutes both surface and subsurface water sources, as well as other products that contribute to air pollution. When people or animals breathe in contaminated air, it can lead to infections and diseases that take a long time to show symptoms. These pollution problems are related with the degradation of cassava peels in dumpsites, and the impacts of these pollution problems include a foul odour and, at times, poisonous and polluted air. In a similar vein, the plants and soil in the area surrounding the dumpsites for cassava peels are rendered unproductive and devasted as a result of the biological and chemical reactions that take place during the breakdown of cassava peels. Peels from cassava roots have been utilised as a source of nutrition for a variety of animals. In addition, cassava peels have been put to use in the manufacturing of reducing sugar, bioethanol, biogas, and biofertilizer (Aisien et al., 2010; Anaeto, et al., 2013; Kongkiattikajorn and Sornvorawea, 2011; and Olanbiwoninu and Odunfa, 2012).

For the purpose of producing biogas, numerous types of research have been conducted, both with cassava peel waste on its own and with cassava peel waste combined with other waste materials, particularly animal waste.
Researchers Adelekan and Bamgboye (2009) and Ofoefule and Uzodimma (2009) found that combining cassava peels with a variety of animal wastes resulted in a considerable increase in the amount of biogas produced as well as the amount of methane yield. They also noted that the ratio of cassava peels to animal waste, also known as the carbon to nitrogen ratio, was highly critical to assure improved generation of biogas and methane yield. Specifically, the ratio of carbon to nitrogen. In addition to this, Ezekoye and Ezekoye (2009), Ilaboya et al. (2010), Ilori, et al., (2007), and Adeyanju, (2008) all reported that the mixing of cassava peels with the waste from other plants was effective. They discovered that there is a requirement to apply some tiny quantity of animal wastes as inoculum in order to achieve an appreciable rise in biogas production and methane yield. This is necessary in order to produce an increase in biogas production and methane yield. Bayitse et. According to the findings of al., 2014, co-digesting cassava peels with manure results in the production of biogas and biofertilizer by optimising the ratio of carbon to nitrogen. Nkodi et. al., 2018 and Olaniyan, et. According to the findings of al., 2017, the volume of biogas produced from the combination of cassava peels and animal waste is more than that produced from cassava peels alone. Besides, Sawyeer et. al., 2017; Onuorah, et. et al., 2016 and Ben and Michael, 2018 reported that the optimal carbon to nitrogen ratio should be maintained at all times. According to what they said, the ratio of cassava peel to animal waste must be 30 to 20 for the maximum amount of biogas to be produced. Olawale et. et al. showed that the addition of pig waste (animal manure) decreased the C: N ratio of the cassava peels to a value between 20: 1 and 30: 1, which is optimal for the anaerobic digestion of co–substrate. Numerous other researchers have recognised the exceptional quality of cassava peels as a substrate due to the high quantity of cyanide they contain. According to their findings, an appropriate pretreatment method must be utilised for there to be sufficient biogas production from cassava peels (Deepanraj et al., 2014; Nkodi et al., 2016; Mel et al., 2015; Ben and Michael, 2018; Igbum et al., 2019; Onuorah et al., 2016, Shah et al., 2015; Gopinattan et al., 2015). They used a variety of chemical pretreatment procedures, such as the use of alkalis (NaOH, KOH, NaHCO3, Ca(OH)2) of varying concentrations in the maintenance of the slurry or substrate pH in order to achieve optimal biogas generation. On the other hand, the use of a buffer solution was not taken into consideration, despite the fact that we assumed it would be more resistant to change in slurry pH compared to alkalis solutions. In the prior research that was done on the conversion of cassava peels to biogas, one of the flaws that was discovered was that the investigation on the bio-digestion of stale cassava peels was disregarded. The environmental pollution and health hazard that are typically linked with cassava peel dumpsites are typically caused by the stale cassava peels that are abundant in most of the cassava peel dumpsites. As a result, the purpose of this study is to fill in some of these gaps. In addition to the alkaline solution, the utilisation of an acid buffer solution as a pretreatment chemical will be examined. In addition, both fresh and stale cassava peels will be investigated in this project. The conclusion will be reached after a comparison has been made.
In light of this, the primary objective of this research is to investigate the production of biogas from cassava peels utilising pig faeces as an inoculum. This could be a viable alternative source of energy in the future. In addition, the purpose of this research is to establish whether or not the digested sludge produced by anaerobic digestion can be a source of biofertilizer. The objective of this study was to investigate the effect of the nature of cassava peels, (fresh and stale) and the applications of different pretreatment chemicals, (alkaline and acid buffer solutions), on biogas production and methane yield. This was done as a result of the identified gaps in the previous research works on cassava peels for the production of biogas.

According to Aderemi et al. (2009), energy is an essential element in the process of any socioeconomic development and a primary aspect in the process of eradicating poverty in any community. According to Onafeso (2006), the lack of access to a wide range of modern energy services has remained a major impediment to the improvement of important indicators of human development in Nigeria, which is located on the west coast of Africa. At the moment, more than sixty percent of the country’s population relies nearly totally on fire wood for the activities of cooking, heating, and agricultural processing. Products derived from petroleum, such as petrol and kerosene, are characterised by severe shortages and rising prices; the product is currently being sold at a price that is more than 300 percent more than the price displayed at the pump (Anonymous, 2008). In addition, energy, which is necessary for contemporary economies, is either not available or, if it is, it is of low quality or, even worse, it is unreliable, since less than 4,000 MW of the 7,876 MW of installed electrical capacity is being generated (Sambo et al., 2010). This is a problem because electricity is the cornerstone of modern economies.
The advent of mechanisation and automation of food processing activities to operate conveyors, pumps, compressors, and other equipment such as steam boilers, dryers, refrigeration devices, ventilation, and ovens has made the usage of electricity an essential component in the food industry. The non-availability of electricity supply or the poor quality and unreliable nature of electricity supply provided by the Power Holding Company of Nigeria (PHCN) has resulted in an increase in the use of stand-by generators of various shapes and sizes (Adegoke and Akintude, 2000). These generators rely entirely on petroleum products as fuel. In spite of the obvious benefit that these standby generators offer as a reliable solution to erratic power supply, the recurrent perennial scarcity of petroleum products and its rising cost contribute to high costs of production and a loss of competitive advantage of processed foods when placed side-by-side with imported ones (Aderemi et al., 2009). This is despite the fact that standby generators offer a reliable solution to erratic power supply. In addition, the nature of petroleum products is such that they have a finite amount, and the byproducts of their burning are substantial contributors to environmental degradation, climate change, and global warming (Das et al., 2000). According to Goodger (1980), the growing awareness of the limitations of the convectional fuel has increased the growing interest in the search for alternative sources of energy that are cleaner and more sustainable. The wastes are typically disposed of without discrimination in landfills and unauthorised areas, which contributes further to environmental degradation and global warming (Adeola, 1996; Igbinomwanhia and Olanikpekun, 2009). However, biogas, which has a relatively significant comparative advantage due to the country’s huge biomass potential estimated to be about 8 x 102 MJ, offers a promising sustainable solution (Nwoke and Okonkwo, 2006). In order to lessen the current overdependence on fossil fuel, increase the amount of energy that is readily available, and protect the natural eco-system in the face of Nigeria’s enormous potential for biomass production (Garba and Sambo, 1992), biogas technology represents a viable alternative due to the ease with which it can be adapted to rural settings and its relatively straightforward technology. (Diaho et al., 2005). According to Dennis and Burke (2001), biogas is a type of fuel gas that is made up of a mixture of methane (CH4), carbon dioxide (CO2), and traces of other gases. It is produced through microbial activities in anaerobic settings from materials that are capable of biodegradation. According to Merchaim (1992), it is a fuel that is both renewable and of a high grade, and when it burns, it does not produce any soot or particulate matter. According to Nwoke and Okonkwo (2006), the technology of biogas has not yet been properly used in Nigeria and other countries in Africa; however, the technology is widespread in countries such as India, China, Pakistan, the United States of America, and the majority of European countries. Utilisation of biogas as fuel in internal combustion engines have witnessed a substantial breakthrough and improvement over the years (Mitzlaff and Mkumbwa, 1980; Mitzlaff, 1988; Huang and Crookes, 1998; Midkiff et al. 2001; Eshan and Naznin, 2005). Although biogas engines are not currently available in Nigeria markets, the crippling fuel prices and high cost of food processing coupled with the growing problem of food wastes management has remained an intractable national problem The modification of these current engines using rurally adapted technology in order to use biogas produced from these food wastes is a vital springboard for the transition to technology that is friendly to the eco-system and for sustainable rural development.
1.2 PROBLEM STATEMENT
Energy is a critical component in achieving the goals of speeding economic growth, reducing levels of poverty, and generating job opportunities. A recurrent problem with the electrical grid has led to an unhealthy reliance on generators that are powered by fossil fuel. In addition to this, fossil fuel is a non-renewable resource that is rapidly running out and is a contributor to the deterioration of the environment. It is highly appropriate to research the use of biogas produced from food and other biodegradable wastes as an alternative fuel source for internal combustion engines in Nigeria because of the chronic power shortage that plagues the country and the currently lax enforcement of laws governing waste management and the use of generators in the country. These laws govern waste management and the use of generators.
Nearly eighty percent of the population relied on petrol generators as their primary source of independent energy supply. Given that more than 70 percent of the population, or an estimated 150 million people, are engaged in agricultural activities and produce a wide variety of plants and animal wastes, the country has a significant agricultural waste problem. An technique that is sustainable over the long term and may be used to achieve energy self-sufficiency as well as economic growth is one that converts these wastes into biogas energy, which can then be used in an existing petrol generator.
1.3 OBJECTIVES
1.3.1 GENERAL OBJECTIVE
The overarching goal of this project was to modify a petrol generator so that it could be used to produce biogas for the production of lower-priced energy alternatives from waste products generated by the food and agricultural industries.