There is an increasing research interest in biomass as an important renewable and environmentally friendly fuel for generating electricity due to uncertainty in the energy market and the problems of greenhouse gas emissions (Gratitude et al., 2019). Utilizing wood waste as biomass to produce bioenergy has the potential to be a very beneficial solution that will guarantee a sustainable energy source while also lessening the environmental impact of the building sector (Maier, 2022) (Xie et al., 2023). The renewed interest in the use of renewable sources of energy in Nigeria was stimulated by the deficit in power generation and the tremendous surge in its population from 88 million in 1990 to over 200 million in 2020 has resulted in more demand for energy (Akintande et al., 2020). The electric load demand in the country is estimated to be 20,000 MW only, an average of 4,156.5 MW was generated in March 2020, and the Association of Nigerian Electricity Distributors (ANED), the umbrella body of Electricity Distribution Companies, (DisCos) has estimated that Nigeria requires 30,000 megawatts of electricity generation to meet the current demand of electricity by consumers (Izuora, 2022). The shortfall in power supply in the country has negatively affected the national economy and destabilised the domestic and industrial sectors as well as other key sectors such as telecommunication, health, transport, and education. Most homes, universities, and companies generate their electricity, “thereby creating a diesel/ petrol driven economy”. The high cost of energy made some companies fold up while others are in the stage of financial comatose. Although the power sector reform report proposed an increase in power generation from 5,000 MW in 2014 to 40,000 MW by 2020 (Oladipo et al., 2018), this goal seems unachievable due to different disruptions and maintenance problems with the hydro and thermal stations. Most of the hydro-power plants are affected by seasonal fluctuations in water level, coupled with the challenges of obsolete equipment and disrupted operation at the thermal stations occasioned by irregular gas supply due to vandalism of gas pipelines. Therefore, there must be decentralization of power generation by adapting mini-grids suitable for different locations.

Nigeria generated an estimated 1,000,000 cubic meters of wood waste annually between 2009 and 2010, according to studies by (Sambo, 2009), (Ogunwusi, 2014), and (Owoyemi et al., 2016). Of this, sawdust accounted for approximately 1.8 million tons each year, translating to around 4,931.51 tons daily {(Sambo, 2009); (Owoyemi et al., 2016); (Akhator et al., 2017)}. In 2014, (Owoyemi et al., 2016) estimated Nigeria’s wood waste production at about 104,000 cubic meters per day. Additionally, (Okedere et al., 2017) estimated annual sawdust production in southwestern Nigeria alone at 526,650 metric tons. This research is an innovative method for assessing the availability of wood wastes for co-generating electric energy in Ondo State and its environment. Ondo State which is one of the major wood processing states in Nigeria has large quantities of industrial wood wastes because of the high demand for wood products with rapid demographic growth. There were 223 sawmills in Ondo State in 1983, constituting about 21% of the total number of sawmills in Nigeria (Alviar, 1983). The continuous increase in the number of sawmills in the State stabilised the position of Ondo State as one of the largest lumber-producing states in Nigeria. With the present trend of log exploitation exceeding the rate of afforestation and reforestation, there is an imminent wood shortage which can only be averted by improved wood conversion and utilization to ensure that optimum benefit is derived from every wood. Maximizing the volume of lumber recovered from logs with a small quantity of waste will increase sawmills' profitability (Rawat et al., 2023). The factors for measuring the conversion efficiency of a mill include lumber recovery factor (LRF), speed of manufacturing, and grade of recovery (Alagbada, 2021). The LRF indicates the quantity of lumber per unit volume of log, it is defined as the ratio of actual board feet (BF) of lumber recovered per unit volume of log processed. Lumber yield is strongly influenced by log form, log quality, and sawmill characteristics such as the types of machines. The grade of recovered wood is important in the assessment of efficiency in that there may be irregularities in lumber dimension due to improper or faulty sawing and this will affect the unit cost of lumber and its utilization. In Ondo State, improper handling of wood waste poses a major environmental risk. Wood waste management practices, which include the collection, disposal, recycling, and reuse of wood waste, are ineffective and inadequate, as evidenced by the obvious disposal of wood waste on streets, in water bodies, and open air. As a result, there will be a serious threat to the sustainability of Nigerian timber forests, human health, and environmental balance.

The substantial reliance on non-renewable fossil fuels in global energy production and consumption has proven to be a significant obstacle to achieving sustainable development goals (Kanwal et al., 2022), (Jie et al., 2023), (Kocak et al., 2023). Electricity production has been the largest source of emission reductions, with the shift in electricity generation from coal to gas and, in the past decade, to renewable energy (RE) (Caselli et al., 2021). Hence, the utilization of wood waste is a means to improve the management of wood waste. Therefore, the objective of this study was to determine the availability of wood waste across different sawmills in Ondo State that could be used as feedstock in an electricity mini-grid power plant at the Federal University of Technology, Akure. The findings from this assessment provided stakeholders and energy experts with information that further reveals the potential of academic institutions producing RE from the abundance of wood wastes to support national climate goals. The adoption of renewable energy by different institutions becomes essential for reducing their environmental footprint and aligning with Sustainable Development Goals (SDGs) 7 (Affordable and Clean Energy) and 13 (Climate Action).

This study was conducted to assess the availability of wood wastes in Ondo State to ascertain the sustainability of feedstock production for a gasifier plant designed at the Federal University of Technology Akure for generating electricity. Ondo State is situated in the South-western part of Nigeria (5° 45′ N–8° 15′ N, 4° 45′ E– 6° 00′ E), Figure 1). The state has 18 local government areas (LGAs) with a population of about 3,441,024 according to the 2006 population census and a land area of about 14,606 km² {(Commission, 2006) ,(Omonijo & Matzarakis, 2011)}. The State has a tropical wet-and-dry climate with an annual rainfall range of 1,500 mm to 2,000 mm in the derived savannah and humid forest zones, respectively. Ondo State is one of the major wood processing states in Nigeria. This is a result of the availability of forest resources feeding its numerous sawmills and other wood processing industries.

This literature review (Table 4) highlights the critical role of renewable energy sources and sustainable practices in addressing global energy and environmental challenges. Renewable power sources are increasingly recognized as viable solutions to reduce dependency on fossil fuels and mitigate their environmental impacts {B.P. Economics, 2018; (Newell & Raimi, 2020)}. However, the adoption of energy-efficiency measures is often impeded by high investment costs, a barrier consistently reported across decades of research {(Fleiter et al., 2012); (Hirshberg, 1976); (Faiers & Neame, 2006)}. While sustainable practices such as energy efficiency improvements and waste reduction can lower production costs and enhance resource utilization (Hannan et al., 2020) (Pimenov et al., 2022), the lack of consensus on strategies for implementing RERs remains a significant challenge to achieving the United Nations Sustainable Development Goals (Olabi et al., 2023) (Wang et al., 2022) (He et al., 2022).

In Nigeria, wood waste mismanagement represents a serious environmental threat, despite its abundance (Sambo, 2009) (Ogunwusi, 2014) (Owoyemi et al., 2016) (Akhator et al., 2017) (Nwankwo et al., 2023). Transforming wood waste into biomass for bioenergy presents an opportunity to address this issue while providing a sustainable energy source, particularly in the building sector. This solution is especially relevant in Nigeria, where rapid population growth has led to increased energy demands (Maier, 2022) (Akintande et al., 2020) (Xie et al., 2023) (Izuora, 2022). By integrating innovative energy strategies and resource optimization, institutions in Nigeria can simultaneously tackle environmental challenges and enhance energy security.

Considering the distribution of sawmills in Akure South LGA with the potential of generating high quantities of wood waste in each region, the efficient utilization of this wood waste for energy generation will play a pivotal role in addressing the environmental and energy challenges posed by these regional disparities (Bais-Moleman et al., 2018).

This finding of the sawmill production capacity indicates a notable lack of advanced and high-capacity machinery within the primary conversion stage of mills within the study area. This suggests that their production is on the small to medium production capacity. This is in line with the study of (Kehinde et al., 2010) that both small- and medium-scale dominated sawmills in Ondo and Osun states, Nigeria. On average, less than 10% of these mills are capable of storing more than a thousand logs in their log yards for future production when the harvest of logs from the forest is difficult and the majority of the mills are capable of converting more than twenty logs per day as they depend on individuals and contractor for log supply. The study showed that the supply of logs reduced drastically during the rainy season. It also revealed that log haulage in the state was also affected by Government policy, this is in agreement with the findings of (Omole & Imoh, 2011) that the sustainability of the forest estate is largely dependent on government policy. Majorly, wastes generated from these sawmills are of different mixed species and regarded sawdust as the dominant waste which can be gotten with no cost while others such as slabs, trimmings, and offcuts as residues because of their potential to be reused are made available with a price. This corroborates with the findings of (Ogunbode et al., 2013) and (Akinbode & Olujimi, 2014).

The findings from this study showed that In Ondo State, improper handling of wood waste poses a major environmental risk as wood waste management practices, which include the collection, disposal, recycling, and reuse of wood waste, are ineffective and inadequate, as evidenced by the obvious disposal of wood waste on streets, in water bodies, and open air. This study corroborates the work of (Nwankwo et al., 2023) in Niger State, Nigeria improper wood waste management practices in the state also present major environmental risks. The lack of efficient systems for wood waste collection, recycling, and disposal threatens not only environmental balance but also the sustainability of timber forests and public health. Wood wastes are generated in the day-to-day wood processing activities in sawmills and furniture manufacturing industries (Owoyemi et al., 2016) (Akhator et al., 2017) (Nwankwo et al., 2023). These processing activities range from conversion of logs, ripping, planning, turning and sanding. A very large volume of the log turns out to be wasted during primary conversion as lumber recovered is less than 60% with a significant difference between the types of mills as those with wear-out conversion machines operating on the small scale level tend to produce more waste during conversion. The low mean conversion efficiency of 56% recorded for the mills is in the same range as earlier reports {(Badejo & Giwa, 1985); (Fuwape, 1986); (Oluoti, 2014)}. (Peterson et al., 2015) described that the reduction of the magnitude of wood supply by mills depends largely on the volume and sizes of wood supplied to the mill, and other competing management objectives. These large amounts of wood waste generated during wood processing activities are mostly dumped on allocated sites to decay. This is not the case for developed countries, where all types of waste have designated dumpsites and storage facilities where they are sorted, treated and recycled or reused. For the effective utilization of wood waste in bioenergy generation in Nigeria the waste management definition of (Ormondroyd et al., 2016) must be given full consideration stating that wood waste management is the collection, refurbishing, recycling, reuse and proper disposal of wood residues. Studies have shown that wood waste recycling and reuse will help create a sustainable environment. However, numerous wood mills in Nigeria have yet to adopt advanced processing of wood waste due to the high cost of the technology and the limited financial returns from processed wood waste (Larinde & Aiyeloja, 2014). The study by (Rawat et al., 2023) revealed that maximizing the lumber recovery rate of Cupressus lusitanica in Ethiopia can increase sawmill profitability, reduce climate change impacts, and promote sustainable forestry and biodiversity conservation.

An assessment of sawmills and wood industries in Ondo State reveals that 84% are willing to collaborate with stakeholders who utilize wood waste, particularly sawdust, as raw materials or for waste management purposes. This willingness extends to offering these materials at minimal or no cost to enhance the efficiency and sustainability of waste management efforts. This is in line with the finding of (Nnaji & Udokpoh, 2022-04) that Sawdust is the most common type of wood waste in the Enugu Timber Market, with open dumping and burning being the most prevalent methods of disposal, causing negative environmental effects and health problems. The study of (Rominiyi et al., 2017) agreed that all readily recovered wood waste could be absorbed by the industry for energy supply. This led to greater attention being paid to the possibility of utilising wood wastes in energy generation which otherwise would be wasted. Also, solving the problem of increasing costs, crisis and depletion of energy from conventional sources over the past few years has reawakened interest in the development of alternative sources of energy. (Mydlarz & Wieruszewski, 2022) further explained in their study that sawmills can use wood waste and by-products for energy, promoting a circular economy and economic efficiency, regardless of government decisions when considering the potential and possibilities of using wood waste and wood by-products generated at various stages of production in companies of the wood industry for energy purposes. The article demonstrates that, regardless of government policies on environmental protection, institutions have the autonomy to adopt pro-environmental practices as part of their operations. This study highlights the feasibility of its objective, emphasizing the abundant availability of wood waste in Nigeria. It suggests that institutions such as the Federal University of Technology, Akure, along with other academic establishments, can sustainably generate electric energy entirely from wood waste collected within Akure and its surrounding areas. The supply of logs is limited because of changes in seasons as wood supply to the mills is reduced drastically during the rainy season. The study by (Okon, 2018) states that sustainable wood harvesting in Nigeria's tropical rainforest requires proper management methods, including the construction of landing sites and training for operators, to minimize damage and promote forest regeneration. Therefore, to ensure that the Gasifier runs non-stop, collection of wood waste for feedstock should be done regularly and more vigorously during the dry season and deposited to the three location points (i.e. Akure, Ikare, and Ore) and move on schedule from the two outer locations to Akure. Regular stocking will ensure enough materials are in stock for use during the rainy season when sawmill activities are at the lowest ebb.

The production and utilization of alternative energy sources are increasingly gaining attention. With traditional energy sources like gas, oil, and coal being non-renewable and finite, the need to explore sustainable alternatives has become more pressing. The abundant generation of wood waste in Nigeria presents a significant opportunity for institutions like the Federal University of Technology, Akure, to establish a reliable source of renewable energy. With proper collection, processing, and utilization of wood waste, including sawdust and offcuts from local sawmills, the institution can create a sustainable energy system that addresses both environmental and energy challenges. This approach not only reduces dependence on non-renewable energy sources but also mitigates the environmental hazards associated with improper wood waste disposal, such as pollution and deforestation, positioning the institution as a leader in renewable energy innovation. (Farjana et al., 2023) described that all wood wastes have great potential to produce energy while reducing climate change impact, with hardwood and softwood products showing the most beneficial aspects. Carbon dioxide emissions from traditional energy sources are significantly higher than those from biofuels, making them a promising alternative energy source {(Farjana et al., 2023); (Opara, 2021); (Kim & Song, 2014)}.

The generation of wood waste is inevitable but can be reduced through improved management techniques. This study revealed that a larger percentage of the sawmills in Ondo State operate on a small scale and generate large quantities of waste daily. The seasonal variations in the volume of log conversion affected the volume of wood waste.

The result showed that 40 to 44% of the total volume of a log converted in the mills ends up as wood waste. The high quantity of wood waste and low lumber recovery were functions of the shape of the log, the size of the log, and the conversion technique. The sawmills in Akure South local government have the highest log conversion capacity and the largest quantity of wood waste. The high values of wood waste generated per sawmill and low values of lumber recovery implied that the log conversion technique in the state is generally poor. This wood waste generated is also not efficiently managed for optimum utilization. Most of the mills regarded only sawdust as waste while other residues such as wood cut-off, slabs, and bark of logs of woods are sold out. The sawdust is disposed of at low costs for domestic uses, dumped in landfills, or burnt at mill sites. This study confirmed that the wood wastes can be used as feedstock in the mini-grid gasifier for generating electricity at the Federal University of Technology, Akure.

The authors acknowledge the Tertiary Education Trust Fund (TETFund-NRF), Nigeria, for financial support.