Rice processing is an important part of Nigeria’s agricultural sector and has the potential to bring significant value to the country. Rice is a staple food in Nigeria and an important food and calorie source for the population. The majority of Nigerians, regardless of ethnic group, rely on rice for their daily diet [1]. Eating one cup of rice (65 g net weight) provides 53 g of carbohydrates. This corresponds to 23.6% of the daily carbohydrate requirement and 10.6% of the daily energy requirement of 2000 calories ^[2][3][2,3]. The reason is that processing promotes local production and consumption of rice. Processing rice can add value to the grain and reduce post-harvest losses. Danbaba identified this as the main cause of rice shortages in Nigeria [4]. Danbaba further clarified that in 2022, not all of the 8 million metric tons (MT) of milled rice, which was consumed at 34.5 kg per capita, was produced in Nigeria [4]. This supports Foyekus’ claim that 44.0% of the 7 million MT of milled rice demanded and supplied in Nigeria in 2018 were imported from other countries [5]. Rice processing or milling is a combination of operations that turn paddy into high-quality white rice and is highly dependent on processors’ management capabilities [6]. In their study, they found that small-scale rice processors were relatively young (36–45 years old), with 11–15 years of processing experience [6]. This level of experience is sufficient to make the farmers understand the basics of small-scale rice processing in the study area. They pointed out that a large household size of 6–10 people lowers the cost associated with wage labor. Ibitoye et al. outlined the steps involved in rice processing from the paddy stage as cleaning, hulling, milling, polishing, grading, sorting, and packing [6]; equally, the returns from small-scale rice processing in their study were affected by the education level and labor availability through a large household size.

The United States Agency for International Development (USAID) submitted that the majority of rice processing in Africa is carried out by small farm-level processors [7]. To date, much of the research has focused on smallholder rice production, with a few studies directed towards milled rice processing in Nigeria. Even the few experts on rice processing focus on profitability rather than looking at the efficiency of the rice industry, which can help policymakers to understand the level of loss in the sector. A study by Akolgoa and Asumboya reported that rice processing is highly profitable and education level has a significant impact on a processor’s profits [8]. Rice processing will help improve Nigeria’s economic stability and the livelihoods of those who depend on the business for survival. Rice processing also has the potential to create jobs within the country and generate additional income for farmers who are in the business of small-scale rice processing options. This will help to reduce poverty within the country and improve the overall standard of living. Rice processing can help reduce the cost of the crop, improve shelf-life, and make it more affordable to the general public [9]. In addition, processing rice can reduce the environmental impact of harvesting. A more efficient processing machine can reduce water and energy usage and reduce the amount of waste. This helps reduce the overall environmental impact of processing activities and ensures that rice remains a sustainable food source for people [10]. Some of the environmental impacts of rice processing include the burning of rice husks, greenhouse gas (GHG) emissions, and the burning of firewood that is unsafe for environmental sustainability [11].

2. Small-Scale Rice Processing

The classification of an enterprise based on size is a reflection of its production and sales turnover, number of employees, and amount of capital investment ^[12][13][14][24,25,26], among others. Small-scale operators have fewer than 250 employees on their payroll ^[15][27]. However, small-scale rice processing involves activities such as drying, cleaning, husking, grading, and polishing to convert a raw grain into a value-added product. This process increases the value of the rice by removing the inedible husk as well as any foreign material that may be present. Rice is a staple food for over 50.0% of the world’s population and is an important part of global nutrition projects ^[6][16][6,28]. Involvement in small-scale rice processing could benefit a rural farmer’s income. By converting raw grain into higher-value products, farmers can avoid the huge markups typically charged by millers, which leaves them with more money to support their families. Additionally, by having the option to process rice, farmers can determine the quality specifications to ensure their rice meets the standards of customers. Despite the high-income opportunities, there are many obstacles to starting a small processing rice business. From a technical perspective, most small-scale operators lack the necessary technology and skills to process rice properly ^[17][29]. There is also a need to raise capital to pay for the necessary equipment to ensure operational efficiency. Additionally, the market needs to be developed for small millers to take advantage of the new value-added products. However, many governments and NGOs are working to support small-scale rice processing projects to empower local farmers, improve incomes and livelihoods, and increase food security ^[18][30]. With proper training, infrastructure, and access to finance, small-scale rice milling can be a viable business opportunity for rural farmers. Furthermore, rice processing is typically carried out either manually or mechanically. Manual processing involves the use of traditional tools and techniques to hull, husk, polish, and mill the rice ^[19][31]. This process is labor-intensive and time-consuming and typically results in a low-quality product [9]. Mechanical processing, on the other hand, employs modern machinery and equipment to efficiently and quickly process the rice. This method of processing is much faster and results in superior-quality products. Despite the obvious advantages of mechanical processing, most rice processing in Nigeria still relies on manual methods ^[20][32]. This is due to several factors including a lack of access to the latest technology, limited resources, and a lack of technical expertise. As a result, the TE of rice processing in Nigeria is much lower than it could be.

3. Technical Efficiency of Small-Scale Rice Processing

TE is an important factor in the success of small-scale rice processing in Nigeria. It is critical for achieving higher yields, improving product quality, and reducing production costs. Unfortunately, TE in the sector is low, with much of the existing equipment being outdated ^[21][33] and inefficient. This has resulted in reduced yields, higher production costs, and ultimately lower profits for small millers. Md. Abu et al. described TE as a firm’s capacity to attain maximal output from a fixed set of inputs ^[22][34]. Ehirim et al. preferred to view TE as the extent to which time, effort, or cost is well managed for an intended task or purpose ^[23][35]. The study by Diarra et al. reported that TE of small-scale rice processing ranges from 65–70% ^[24][36]. Similarly, Asmiya and Sivarajah reported a shrinking TE value of 60% among small-scale rice processors ^[25][37]. These statistics validate the need to promote government interventions in the agricultural sector. Several steps can be taken to improve TE of small-scale rice processing in Nigeria; this is because improving efficiency is proportionate to an improved standard of living ^[26][27][38,39]. The first step is to invest in modern and efficient equipment. This includes replacing old and inefficient machines with modern versions that are designed to reduce energy consumption and increase throughput ^[21][33]. It also includes investing in appropriate tools, such as polishers and hullers, that can help to improve the quality of the final product. In the next step, it is important to ensure that small-scale processors have access to the necessary technical expertise. This includes training in the latest techniques and technologies, as well as support in troubleshooting and maintenance. This is particularly important in rural areas, where access to technical support is often limited. Furthermore, it is important to ensure that small millers have access to the necessary resources. This includes access to credit and other financial support, as well as access to spare parts and other items that may be needed for repairs and maintenance. By providing these resources, small millers will be able to effectively access the capital and resources needed to improve their efficiency. In conclusion, improving TE in small-scale rice processing in Nigeria is essential for ensuring the sector’s long-term success. By investing in modern, efficient equipment, providing access to technical expertise and resources, and supporting small millers in their efforts to improve efficiency, the sector can be well on its way to achieving greater success. This assertion supports the statement by Diosdado and Biley that the level of technical know-how and technology adoption affects the efficiency of production ^[28][40]. Many works on TE were conducted in the field of rice production, though none has been established on small-scale rice processing in the study area. Ehirim et al. found the TE of rice farmers in their study to 0.47 ^[23][35]. Md. Abu et al. reported 0.80 for submerged rice production, 0.77 for drought, and 0.74 for saline rice production ^[22][34]. Mohammad et al. found a TE of 0.75 in their study for rice production ^[29][41].

4. Technological Gap Ratio (TGR) in Small-Scale Rice Processing

Small-scale rice processing in Nigeria is becoming increasingly efficient as the country looks to capitalize on the growing demand for locally-produced rice. In recent years, there has been a focus on improving the TE of small-scale rice processing to ensure that more value is added to the product, thereby increasing the profitability of production. The TGR in small-scale rice processing in Nigeria is a major cause for concern. TGR measures the ratio of the output for the frontier production function in a group relative to the potential output which is defined by the meta-frontier function of observed inputs ^[30][31][42,43]. In Nigeria, it is estimated that 85% of rice is produced by smallholder farmers; however, these farmers are operating with outdated technology and are unable to meet the demands of an ever-growing urban population ^[32][44]. This is resulting in a significant gap between the productivity of smallholder rice farmers, processors, and their urban counterparts. The TGR in small-scale rice processing in Nigeria is attributed to several factors, including a lack of access to modern technology, inadequate extension services, and limited access to credit and other inputs. Recently, some scholars defined TGR as the gap between the production technology adopted by rice farmers and the technology available ^[33][16] in the rice industry. They assumed that a TGR of one implied that the farmers adopted the most advanced technology available, whereas Ng’ombe ^[34][12] and Korotoumou et al. ^[35][45] submitted in their study that a ratio of less than one means that the farmers failed to adopt the most advanced technology. Small-scale processors are often unable to invest in better-quality equipment and there is a lack of knowledge regarding modern techniques. This leads to a lower production output and a higher rate of wastage. Furthermore, the lack of access to credit and other inputs has created a situation where small-scale processors are unable to take advantage of the opportunities presented by the market. Additionally, the lack of access to modern technology has led to an increase in the cost of production, which, in turn, has decreased the competitiveness of small-scale processors. The gap in small-scale rice processing in Nigeria needs to be addressed to ensure that processors can compete in the market and increase their productivity. To this end, the government must provide support to small-scale rice processors in the form of access to modern technology, training, access to credit, and other inputs as part of the objectives of VCDP. The technological gap in small-scale rice processing in Nigeria is a major cause for concern and requires urgent attention from the government and other stakeholders. If the gap is not addressed, it will continue to affect the productivity of small-scale processors and the competitiveness of the rice market in Nigeria.

5. Meta-Technical Efficiency (MTE) of Small-Scale Rice Processing

Small-scale rice processing in Nigeria is becoming increasingly popular as a way to reduce post-harvest losses, improve farm incomes and increase food security. The ability to process, store and transport rice more efficiently is a key factor in improving the overall efficiency of small millers. MTE is an important component of small-scale rice processing, which is defined as an effective use of technology and other resources to facilitate the production process. Kanis et al. ^[36][46] noted that MTE is used to assess how efficient different firms in Bangladesh are in their operation or processing activities. MTE is a key component to reduce post-harvest losses and increase productivity, as it allows for better utilization of resources and improved quality control among different groups involved in rice processing. MTE can be improved through the use of modern processing and storage technologies, such as automated rice mills and grain silos. Automated rice mills can reduce post-harvest losses by 17–30% [4], while grain silos can provide a safe and efficient means of storing rice for a long period. Additionally, the use of modern processing technologies can reduce labor costs, improve product quality and reduce waste. Being that this is the first time the meta-stochastic approach is used to assess small-scale rice processing actors in Anambra State VCDP, the authors likened this research to the work by Xiangfei et al. ^[37][47], who viewed MTE as a structural change analysis. In addition to the use of modern technology, other measures can be taken to improve MTE in small-scale rice processing. These include the adoption of good agricultural practices (GAPs), the establishment of quality assurance systems, and the implementation of effective monitoring and evaluation mechanisms. GAPs can help to ensure that the process is conducted safely and efficiently, while quality assurance systems can ensure that the products meet the required standards. Finally, monitoring and evaluation mechanisms can help to identify areas for improvement. MTE is, therefore, an important factor in improving the overall efficiency of rice processing in Nigeria. The above statement pointed to the assertion by Nan and Basil ^[38][48], who noted that MTE is a procedure developed to determine whether technology adoption differs among firms.

6. Challenges of Rice Production and Processing in Nigeria

One of the main challenges of rice processing value chain is inadequate infrastructure. Many African countries lack the basic infrastructure needed to transport and store the harvested rice, meaning that most of the rice is left to rot in the field or sold to traders at a low price. This is compounded by the lack of resources within the industry, with many small rice millers not having the funds to purchase the necessary equipment for processing ^[39][49]. Again, access to market is a major issue for the rice processing value chain in Africa. Limited access to market particularly in rural areas, means that farmers are unable to sell their rice at a fair price. This in turn leads to selling the rice to traders at much lower prices than they would have if small millers were able to access larger markets. Ampadu-Ameyaw et al. ^[40][50] believe that participants in the rice value chain need training. The study by Sennuga et al. ^[21][33] further itemized some factors that militate small-scale rice processing as:

• Lack of infrastructure: inadequate roads, rail, or water infrastructure to facilitate the transportation of paddy and milled rice to and from production sites makes it difficult to efficiently source and distribute rice.
• Poor milling capacity: there are inadequate modern rice mills in Nigeria and the existing ones are using outdated, inefficient technology, which makes the milling process slow and costly.
• Inadequate storage and preservation facilities: poor storage and preservation infrastructure prevent the effective use of modern storage technologies, leading to a significant loss of paddy and milled rice due to deterioration and spoilage.
• Low yield and productivity of farms: Nigerian farmers continue to use traditional methods of cultivation and low-yielding varieties of rice, which reduces potential yields.
• Lack of access to finance: small-scale rice processors often lack access to the credit and capital needed to purchase the necessary processing equipment to improve their operations.
• Environmental degradation: unsustainable methods of rice farming have led to serious soil and water degradation in many areas, leading to reduced productivity.
• Increasing competition from other countries and imports: rice importation increased since the 1990s, causing the local industry to suffer. With these challenges, the rice industry is growing, with many public and private initiatives being put in place to improve yields and processing. Similarly, with the right investment and innovation, the industry has the potential to substantially increase its production to remain competitive in regional markets.
• Skills and technical know-how: even with the help of the government, which provided few processing machines at a subsidized price, the processors still need training on how to operate the machines.
• Limited access to information and innovation: the inability to get timely information about innovation by the rice processors is also a constraint to the processing of rice because processors are not up to date about the newest and latest method of processing; this could be attributed to the inability of the extension advisors to quickly locate smallholder farmers and small millers with information on current events in the industry.