Improving Poultry Waste Management for Energy Production in Nigeria: A Case Study of Poultry Management Systems in Selected Local Government Areas of Anambra State, Nigeria

Agriculture is the mainstay of Nigeria’seconomy, employing more than two-thirds of her total active labour force and has been contributing more than 42.2% of her gross domestic product (GDP). Also in 2007, agriculture provided about 88% of the country’snon-oil earning. However, despite all these achievements, animal protein especially meat is expensive, in short supply and out of reach of the majority of the population. Thus, most of the people get far too little of these nutritious and protective foods such as meat and eggs that are required for normal growth, energy and resistance to various diseases (Chukwuji et al, 2006). The effect of this inadequate meat intake is felt more by a large proportion of the population especially in rural areas, where inhabitants constitute over 70% of Nigerians who constitute about 85% of the extreme poor in the country (Anosike et al, 2015).

The term poultry generally used in agriculture refers to all the domesticated birds kept for eggs or meat production. These include chickens or domesticated fowls, turkeys, ducks and geese. However, atimes the term poultry is seen as being synonymous with chickens. The rising standard of living in the country has resulted to rising demand for eggs and meat. Meanwhile, the fact that people cannot raise their own poultry has called for more establishments of poultry farms in the country. Under this system, birds are kept in runs made of wire-netting where they can move about in the runs during the day but are kept in poultry house at night.

Poultry meat and eggs playa very useful role in bridging the protein gap in Nigeria (Nwagu, 2002). The total poultry bird population in Nigeria reached a total of 169 million heads in 2021 (Doris, 2023; Ajala et al, 2007), same as the count of the preceding year, however, the count observed that within the period, the highest stock of live poultry birds in the country was registered in 2018 which stood at 184 million birds. The Nigerian poultry industry has been contributing approximately 25% to her agricultural GDP; and since 2008, there has been a deliberate national drive to promote agriculture as business. But Adedotun (2002), noted that despite the expansion of the poultry industry in recent years, poultry farming in the country only caters for about 30% of chicken eggs and meat needs of Nigerians, which amounts to about 300metric tons and 600metric tons of eggs respectively per year. The poultry industry in Nigeria is worth about N1.6tr, making it the most commercialized sub-sector of all Nigeria’sagricultural sub-sector (Emefiele, 2019; FAO, 2019; Udo et al. 2006; PAN, 2017; Adene and Oguntade, 2006; World Bank, 2005). There is consensus that about 90% of the figures derived from the local poultry stocks are composed of chickens (91%), guinea fowl (4%), duck (3%), turkeys and others (2%). 1.1 Poultry Management: Depending on the purpose for which the birds are reared, and available capital, there are various methods of poultry management: 1.1.1 Intensive Systems: In this system, the birds are kept indoors all the year round. More fowls can be kept in a small area of land than under the semi-intensive or free range systems. There are different methods or intensive management systems. 1.1.2 The Fold System: Under fold system, the birds are kept in moveable houses which allow the birds certain amount of freedom. Thus, this method is successful where land is clear and well-drained, with good pasture, however, the system is very expensive and demands much attention. 1.1.3 Deep Litter System: In this system, birds are kept in as completely closed but well-ventilated house where they are fed. The birds are kept indoors all the time on a layer of litter made of absorbent materials, such as straw, saw dust, or wood shavings, which absorbs the liquid droppings of the poultry. It is essential that the house is airy and cool, providing about I sq. mspace per bird for light breeds and about 1.3 sq.mspace for birds for heavy birds.

Inside the deep litter house, feeding and drinking troughs are necessary, as well as suitable length of perch on which birds can rest at night. Both feeders and drinkers should be moveable, and should be kept not less than 46 cm high such that birds cannot perch on them or defecate into them this is to avoid feed wastage or spread of disease. 1.1.4 Battery Cage System: Birds especially layers can be kept in battery cages made of galvanized wire. The birds may be kept single in each cage or ingroups of two to four.Some battery cage systems permit automatic supply of both feed and water and egg collection while other operations can be carried out manually. This system allows poultry droppings to fall through the wire at the bottom of the cage from where the can be cleared away. 1.1.5 Free Range System: In free range system, birds are allowed to roam freely about under natural conditions and feed themselves. However, this system exposes the birds to the dangers of wild animals and theft. 1.1.6 Semi-intensive System: 1.2 Types of Chicken: Although there are many different breeds of chickens used in poultry farming, they all can be divided into three types: 1.2.1 Layers: These breeds primarily are for egg production. These birds usually weigh about 1-2 kilograms. They are lighter than chicken bred used for meat production, and they needless feed to maintain their body weight while laying as many or more eggs than the big birds. 1.2.2 Meat Chickens: These types of chicken grow very rapidly and reach marketable size after two to three months, and are commonly called broilers. However, their size and age determine whether they are called a fryer or a roster. 1.2.3 Dual-Purpose Chickens: These birds are raised for both their eggs and meat. Females of the new, improved breeds are kept to lay eggs while the males are separated and sold for meat as soon as they reach about 15 weeks of age. 1.3 Basic Requirement for Poultry Housing: There are some important basic requirements for poultry housing such as: space, ventilation, light, and protection. 1.3.1 Space: Space is most important basic requirement for poultry housing as it determines the number of poultry that can be kept (Chukwuji et al. 2006). For instance, a deep litter size of 6m x 11m can hold 200 laying hens at stock density of 3 birds/m2. (3.6 ft2/bird), while the recommended requirement for chickens for floor and perch space is presented in Table 1. Less space creates stressed social behaviour which encourages disease vulnerability and cannibalization, weaker birds deprived of feed or perch space (Sonaiya, 2000; Ugwu, 1990; Adeyemo and Onikoyi, 2012).

TABLE 1 REQUIREMENT OF CHICKEN FOR FLOOR AND PERCH SPACE.

Chicken Types Floor Space (Birds/m2) Floor Space (ft2/Bird) Perch Space (per Bird)

Layer 3 3.6 25 cm (10 in)

Dual purpose 4 2.7 20 cm (10 in)

Meat 4 – 5 2.1 – 2.7 15 – 20 cm (6 – 8in) 1.3.2 Ventilation: A building with open sides is ideal, otherwise cross-ventilation at bird-level should be allowed for in the form of floor level inlets, open in a direction to allow the prevailing wind to blow across the width of the building. Heat stress can lead to death of the birds. Birds can withstand several degrees below freezing point, but cannot tolerate temperature above 40OC (Feddes et al. 1992; Kocaman et al. 2005; Salum et al. 2002). Building materials such as tin or other metal should be avoided for this reason. Heat stress affects the birds in several ways: i. Reduction in feed intake as ambient temperature rises. ii. An increase in water consumption in an attempt to lower temperature. iii. A progressive reduction ingrowth rate. iv. Reduction in rate of laying eggs 1.3.3 Light (Duration and Intensity): A well-lit house is essential for birds as a dark house leads to lethargic, inactive and unproductive (Kenneth and Larry, 1981). Light is important for feeding, increased egg production, thus regular and reliable electricity supply is required. 1.3.4 Protection: There are many factors that affect the type of houses. Birds need to be properly housed to protect them from adverse effect of weather or predators. These factors include local climate, space, size and number of the flock, and management system (Onwualu et al. 2006). In extensive systems, birds must be protected from disease and predators such as snake, kites, rats, theft, and other vermin (Conroy et. al. 2005; Sonaiya et. al. 2004). 1.4 Poultry Waste: Poultry raised for commercial purposes produce large amount of wastes which contain valuable plant nutrients and other chemicals that if properly managed, can be returned to the landor processed for other uses. 1.5 Production of Biogas from Poultry Waste: 1.5.1 Definition of biogas: Biogas is a flammable gas produced when organic materials are fermented under anaerobic condition. It originates from biogenic material and it is a type of bio-fuel (Ghosh, 1997; Jenner, 2006). Biogas has globally remained a renewable energy source derived from plants that use solar energy during the process of photosynthesis. Being is source of renewable natural gas; it has been adopted as one of the alternatives to fossil fuels after 1970’sworld energy crisis. Biogas is a product of the metabolism of methane bacteria and is created when bacteria decomposes amass of organic materials. It is smokeless, hygienic and more convenient to use than other solid fuels. To produce biogas, water is added to animal/plant waste in a certain ratio to form slurry and digestion takes place in the process of anaerobic digestion. Anaerobic digestion (AD) is a microbial process in which micro-organisms breakdown and organic waste because it provides volume and mass reduction of the input material. Anaerobic digestion is also a biological process in which organic material is decomposed in the absence of oxygen to produce biogas. The organic matter can be degraded by the sequential action of hydrolytic, acetogenic and methanogenic bacterial to produce biogas.

Biogas is a colourless, flammable gas produced through anaerobic digestion of animal, plant, human, industrial and municipal waste amongst others. It is composed of methane (50-70%), carbon dioxide (20-40%), water vapour (2-7%), and traces of other gases such as ammonia, nitrogen, hydrogen, hydrogen sulphide as shown in Table 2 below.

TABLE 2 COMPOSITION OF BIOGAS Component Concentration by volume (%)

Methane (CH ) 50 – 70 4 Carbon Dioxide (CO ) 20 – 40 2 Water (H O) 2 – 7 2 Hydrogen Sulphide (H S) 2 2 Ammonia (NH ) 0-0.55 3 Nitrogen (N) 0 – 2 Oxygen (O ) 0 – 2 2 Hydrogen (H) 0 – 1 Source: Mattocks, (1980)

Biogas technology is a biochemical conversion technology of bio-energy conversion where decomposition or degradation of organic matter occurs in the absence of oxygen by microorganisms (Legett, 2006). Biogas technology is based on the phenomenon that when organic matter containing cellulose is fermented in the absence of air (anaerobically), combustible gases (chiefly methane) are emitted. Biogas technologies commonly apply consortia of microbes. These communities form an intricate microbiological food chain. 1.5.2 Bases for Biogas Technology: Biogas is produced by the biological breakdown of organic matter in the absence of oxygen. It originates from biogenic material and is a type of bio-fuel. One type of biogas is produced by anaerobic digestion or fermentation of biodegradable materials such as biomass, manure or sewage, municipal waste, green waste and energy crops. This type of biogas comprises primarily of methane and carbon dioxide. The other principal type of biogas is wood gas which is created by gasification of wood or other biomass. This type of biogas is comprised primarily of nitrogen, hydrogen, and carbon monoxide, with trace amounts of methane.

Biogas generators or digesters yield two products: The biogas itself and a semi-solid by-product called effluent or sludge. Biogas systems are most popular for their ability to produce fuel from products that might otherwise be wasted crop residues or manures. The fuel is a flammable gas suitable for cooking, lighting, and fuelling combustion engines. 1.5.3 Formation of Ammonium Fertilizer from Poultry Waste: The digested waste or sludge is a high-quality fertilizer. The digestion process converts the nitrogen in the organic materials to ammonium, the form in which it becomes more stable when ploughed into the soil. Ammonium is readily fixed or bonded in the soil so that it can be absorbed by plants. Moreover, biogas systems offer a need to sanitize wastes. Thus, the systems are capable of destroying most bacteria and parasitic eggs inhuman and animal wastes, enabling the digested sludge to be applied safely to crops. 1.5.4 Biogas models: The development of biogas plant that co-digests agricultural waste with other organic wastes, energy crops or industrial wastes has been aggressive over the past two decades. This is as the result of economic, social and environmental pressure. The Kyoto Protocol, which requires countries to meet 1990 levels of greenhouse gas (GHGs), is avery significant driver (Energy Commission of Nigeria, 1998 In Europe, Denmark has been the world leading country in anaerobic digestion development and implementation, especially for generating manure for fertilizer and for electricity production. One of the driving forces in Denmark is their goal of achieving 33% of their total energy requirement to be derived from renewable energy sources by the year 2030. Biogas generators or digesters operate throughout Asia, for example, more than 100,000 biogas generators or digesters have been reported to be in use India, about 30,000 in Korea, and several millions in China. Ancient Chinese experimented burning the gas given off when vegetables and manures were left to rot in a closed vessel (Nwoye et al. 2014; Chukwu et al. 2006).

Presently, China has successfully promoted the use of biogas as a source of household energy since 1980s, especially in the rural areas where wood for fuel was in short supply and rural electricity was not available. Each household builds its own plant to channel waste from the domestic toilet and nearby shelters for animals, usually pigs, into a sealed tank. The waste ferments and is naturally converted into gas and compost. In addition, the project has resulted in better sanitary conditions in the home. In Nigeria, biogas technology can serve as a means to overcome energy poverty, which poses a constant barrier to economic development in Africa, (Chukwuma et. al., 2021). Biogas production from energy crops, agricultural wastes, industrial wastes, municipal water, crop residues etc., does not compete for land, water and fertilizers with food crops like is in the case with bio-ethanol and biodiesel production. 1.5.5 Biogas technology in Nigeria: Anaerobic digestion has been deemed one of the most useful decentralized sources of energy supply by the United Nations Development Programme. In United States of America, Europe and Asia, there has been considerable interest in the process of anaerobic digestion as an approach to generating a safe clear fuel as well as source of fertilizer (Chukwuma et al. 2013; Umeghalu et al. 2015). In the past decades, the consumption of poultry in Nigeria and in many other countries has been on the increase. Growing demand for poultry product has resulted to corresponding increase in the poultry industry and consequently increased amount of organic solid by-products and wastes. It was reported that annually about 724.8 tons of poultry droppings and 184,128 tons of paunch are produced from poultry farms and from cows slaughtered in major abattoirs respectively in Anambra State of Nigeria (Umeghalu et al. 2012). Only a small proportion of the poultry droppings generated in major farms in the state is utilized for manure application (majorly during planting season) and fish farming. Poultry droppings can be considered as a sustainable biomass. The rapid growth of poultry industry in the country has been causing increasing concern about the disposal of poultry wastes with respect to non-point source pollution. The management of poultry waste constitutes a major problem in poultry industry (Umeghalu et al. 2012; Chukwuma et al. 2012).