Capital costs included one-time investments required for facility construction, equipment acquisition, and site preparation. These encompassed expenses such as fermentation tanks, distillation columns, molecular sieves, ethanol storage tanks, piping systems, and steam boilers [22] . The required fermentation tank capacity was estimated using:

$V_c\text{}=\frac{Q·D}{t_w}$ (1)

Where:

Q is the total bioethanol production volume per year (L/year).

D is the number of operational days per year (300 days/year).

$t_w$ is the plant’s working hours per day (24 hours/day).

$V_c$ is the fermentation tank capacity or volume

The calculated $V_c$ value was used to estimate the construction costs (CC) using Equation (2)

$CC=V_c·C_p$ (2)

where:

$C_p$ is the unit cost of constructing a fermentation tank (obtained from supplier quotes).

Figure 1 shows the flowchart outlining the stepwise methodology used in the study

The machinery and equipment costs include fermentation tanks, distillation columns, molecular sieves, ethanol storage tanks, pumps, and steam boilers. These costs were calculated based on the plant’s required production capacity and quotes from suppliers.

Additional costs, such as electrical wiring, piping, and site works, were factored in using coefficients derived from previous studies. Land acquisition was estimated at 1.5% of the total capital investment costs. Contingencies, contractor charges, and engineering consultancy fees were estimated as percentages of the total construction cost [23] .

Operational costs included feedstock procurement, energy consumption, labor, water, maintenance, and taxation. The plant required 200 tons of corn stover per day, with energy consumption evaluated based on the power demands of distillation, fermentation, and cooling systems [24] . Process water requirements were determined by considering usage in feedstock preparation, fermentation, and cooling processes. Maintenance and repair costs were estimated at 1.5% of the total capital costs, while government taxes and worker salaries were estimated at 1% and 2%, respectively [25] .

Optimization strategies were integrated to reduce operational costs, including bulk purchasing agreements for feedstock and energy-efficient technologies to lower electricity consumption [26] . Efforts to optimize operational costs included reducing feedstock costs by negotiating bulk purchase discounts and implementing energy-efficient technologies to lower electricity costs.

The revenue projections considered income from bioethanol sales and by-products, such as carbon dioxide for industrial applications and residual biomass for animal feed. The economic benefits of the plant include revenue from the reuse of treated process water. Sensitivity analyses were performed to evaluate financial risks under market fluctuations, with adjustments for inflation and taxation [27] .

Several tools for economic evaluation were used to present a comprehensive view of the investment costs and benefits of the project. The fundamental tools included Net Present Value (NPV) and Payback Period (PB), which help determine the financial viability of bioethanol production. The NPV reflects the project’s profitability by discounting future cash flows, while the PB assesses the duration required to recover the initial investment [28] . A shorter PB indicates a more attractive investment., such as carbon dioxide for industrial applications and residual biomass for animal feed. Sensitivity analyses were performed to evaluate financial risks under market fluctuations, with adjustments for inflation and taxation [29] .

This structured TEA methodology provides a comprehensive evaluation of technical and financial feasibility, supporting investment decisions and policy formulation for sustainable bioethanol production. The NPV of a project reflects the worth of the project. The payback period is the time it takes to recover the cost of an investment [30] . It is determined by dividing the initial investment by the average cash flows. A payback period that is shorter, makes an investment more attractive than one that is longer. An average inflation rate in Zambia of 11.04% (average from 2005 to 2024) is used [31] .

$NPV=\underset{t=1}{\overset{n}{{\displaystyle \sum }}}\frac{C{F}_t}{{\left(1+r\right)}^i}-\text{Initial Investmen}$ (3)

Where:

Changing the discount rate used to value future cash flows changes the Net Present Value (NPV) when you use a standard cost of capital. The NPV goes up if the standard rate is lower than the original, which makes the project look better. The NPV goes down if the standard rate is higher, which could make the project less viable. Using a standard rate makes sure that evaluations are consistent, but it might not accurately reflect the risk of a specific project, which could lead to bad investment choices.

The payback period is useful when making investment decisions even though it does not consider the time value of money [32] . The annual profits were calculated by subtracting operational costs from total revenues, and the payback period was determined using Equation (4):

$\text{Payback Period}=\frac{Totalcapitalcost\left(\$\right)}{annualprofit\left(\$/year\right)}$ (4)

The analysis showed that the use of optimized processes, including efficient distillation and dehydration technologies, improved profitability.

Based on market projections for renewable fuel alternatives and regional fuel pricing benchmarks, the ethanol selling price of $1.50 per litre was assumed. This price is consistent with recent developments in the biofuel market in southern Africa, where imported ethanol products range in price from $1.40 to $1.60/L, contingent on blending policy incentives, purity, and grade ( [33] ). This price was also tested across a range of $1.20 to $1.70 per litre to assess the impact on profitability and the payback period, taking into account market volatility and policy changes.

Table 1 provides a breakdown of the expenditure for lab-scale bioethanol production, detailing the costs associated with essential inputs such as enzymes, yeast, fermentation tests, and support staff wages.

This table offers a bill of quantities for various components that are also present in the industrial-scale TEA. The expenditure analysis at this stage helps understand the key cost drivers before scaling up production.

Table 2 presents the TEA for industrial-scale bioethanol production, outlining the capital and operating costs required for a plant with a daily production capacity of 50,000 liters. The capital cost section includes significant expenditures such as fermentation tanks, distillation columns, storage tanks, and process infrastructure. Notably, some items in Table 2 derive their unit costs and justifications from the expenditure analysis in Table 1 , allowing for a more structured cost assessment.

The ever-increasing cost of fossil fuels and the fact that Zambia relies on imported petroleum products necessitate alternative energy solutions. Bioethanol, derived from agricultural residues such as corn stover, presents a viable option for reducing fuel costs, enhancing energy security, and stimulating local economic development. This study evaluated the techno-economic feasibility of bioethanol production, highlighting key cost drivers, the cost per liter of bioethanol, the investment payback period, and the impact of E10 blending on Zambia’s fuel pricing and economy, as well as the environmental impact.

The total capital investment required for a bioethanol production plant with a 50,000-liter/day capacity was estimated at $5.62 million. Figure 2 illustrates the percentage breakdown of capital investments for the bioethanol plant.

The most significant capital cost components were the distillation columns, which account for 22.49% of the total investment, followed by fermentation tanks (11.36%) and construction and installation (12.99%). Molecular sieves for dehydration contribute 6.49% to the total capital expenditure. These figures align with previous studies by [34] , which found that distillation infrastructure remains one of the most cost-intensive elements in bioethanol production from lignocellulosic biomass.

Annual operating costs for the plant amounted to $3.17 million, with the largest expenditure being feedstock procurement and processing at $2.25 million per year (83.67% of total operating costs). Other significant costs included utilities such as electricity and water ($527,870.28 annually) and enzymatic hydrolysis, which accounted for $120,000 per year. Compared with the findings of [35] , who reported enzyme costs as a major limitation in lignocellulosic ethanol production, the use of Deep Eutectic Solvents (DES) in this study significantly reduces pretreatment expenses, thereby lowering overall processing costs.

The cost of producing one liter of bioethanol was calculated at $0.21, making it highly competitive when compared to conventional production methods. Studies by [36] indicated that bioethanol production from agricultural residues typically ranges between $0.35 and $0.50 per liter, demonstrating the economic advantage of the DES pretreatment method used in this study. Revenue from ethanol sales was estimated at $22.5 million per year, based on a selling price of $1.50 per liter, while by-product sales (CO₂, biomass, and treated water) can contribute an additional $900,000 annually. With a net annual profit projected to be $20.23 million, the payback period for the investment was estimated at 2.78 years, significantly shorter than the 4 - 7-year payback period reported by [37] for traditional lignocellulosic bioethanol plants. The reduced payback time highlighted the financial viability of this approach, making it attractive to investors and policymakers. Table 3 shows a concise sensitivity-analysis table summarizing how ±20% changes in key inputs shift the NPV and PB.

The current gasoline retail price in Zambia stands at $1.1724 per liter. With the introduction of E10 blending, the projected pump price for blended fuel was estimated to be $1.0762 per liter, reflecting an 8.2% cost reduction. This price advantage is crucial in making fuel more affordable for consumers. Studies by [38] also confirm that ethanol blending leads to reduced fuel costs and improved energy security, particularly in economies reliant on fuel imports. In terms of fuel substitution, the adoption of E10 blending can displace approximately 44.5 million liters of gasoline annually, reducing Zambia’s petroleum import bill. This shift aligns with global trends, as noted by [39] , who highlighted that ethanol blending policies in emerging economies have successfully reduced fuel costs and foreign exchange expenditures.

It is necessary to recognize possible logistical and policy-related risks that could affect the payback period, even though the techno-economic analysis shows financial viability. Supply chain disruptions, such as a lack of baling equipment, seasonal transportation limitations, or problems with the road infrastructure, can raise the cost of handling feedstock or cause delays in operations. On the policy side, unclear fuel pricing rules, ethanol blending requirements, or incentives for biofuel investors could all slow market demand or postpone revenue realization. These risks could cause the anticipated payback period to be longer than the 2.78-year projection, especially if capital recovery is linked to shaky policy frameworks or inadequate infrastructure. To protect the project’s financial performance, it will be essential to proactively address these factors through stakeholder engagement and supportive national bioenergy policies.

Bioethanol production has the potential to stimulate Zambia’s economy through job creation, value addition, and industrial development. The construction and operation of bioethanol plants can generate employment across multiple sectors, including agriculture, manufacturing, and transportation [40] . Farmers can benefit from increased demand for corn stover, providing an additional revenue stream and supporting rural livelihoods. The economic impact can extend to reducing Zambia’s dependence on imported petroleum, easing pressure on foreign currency reserves. By displacing 44.5 million liters of gasoline annually, the country will achieve significant foreign exchange savings, which can be redirected to other critical sectors such as healthcare and infrastructure development [41] . Beyond cost competitiveness, bioethanol production offers broader economic and policy benefits. The displacement of fossil fuel imports can lead to substantial foreign exchange savings, ensuring greater energy security for Zambia. Additionally, the establishment of bioethanol plants can create employment opportunities across the agricultural supply chain, industrial processing, and logistics sectors.

The adoption of bioethanol-gasoline blends, such as E10, presents a potential strategy for reducing greenhouse gas (GHG) emissions, improving air quality, and enhancing energy security. Bioethanol, derived from renewable biomass, is of a lower carbon intensity than conventional gasoline due to its biogenic carbon cycle [42] . Studies indicate that bioethanol blending displaces high-carbon aromatics in gasoline, contributing to emission reductions [43] . Several countries are reporting lower CO₂ emissions, reduced reliance on petroleum imports, and improved air quality following the implementation of bioethanol blending policies [44] .

Zambia’s gasoline consumption in 2023 was recorded at 445,044.58 metric tons, with estimated CO₂ equivalent (CO₂e) emissions calculated at 1,366,286.86 metric tons (Mutemi, 2022). The introduction of E10 was projected to reduce these emissions to 1,229,658.17 metric tons, representing an annual reduction of 136,628.69 metric tons, or approximately 10%. The extent of this reduction aligns with Zambia’s climate mitigation commitments, suggesting bioethanol’s potential role in national carbon reduction strategies [45] .

The reduction in emissions is attributed to bioethanol’s renewable nature. Unlike fossil-based fuels, bioethanol is produced from biomass, which absorbs CO₂ during plant growth, partially offsetting emissions from combustion. Life-cycle analyses indicate that corn-based bioethanol can achieve up to a 40% reduction in GHG emissions compared to gasoline [46] . Furthermore, E10 blending has been proven to decrease fuel carbon intensity to 43.4 g/MJ or lower, primarily due to the displacement of gasoline’s high-carbon components (Higgins et al., 2023). Since bioethanol combustion is considered carbon-neutral, blends such as E10 and E15 contribute no net additional CO₂ emissions from the bioethanol component [47] .

Apart from GHG reductions, bioethanol blending is linked to improved air quality through the reduction of harmful pollutants, including carbon monoxide (CO), particulate matter (PM), and volatile organic compounds (VOCs) [48] . These pollutants are known to be contributors to urban air pollution and respiratory illnesses. Several studies suggest that the use of bioethanol-blended fuels results in lower concentrations of these pollutants, especially in densely populated areas. Countries with established bioethanol blending programs have reported measurable declines in respiratory diseases associated with poor air quality, suggesting potential public health benefits from bioethanol adoption [49] .

Bioethanol blending has always been associated with economic and energy security benefits. By reducing total emissions, bioethanol adoption can lead Zambia to participate in carbon credit markets, generating additional revenue and attracting investment into renewable energy sectors [50] . Some countries have successfully leveraged carbon credit mechanisms to offset bioethanol production costs and stimulate biofuel industry growth [51] . The economic benefits extend to job creation, industrial development, and value addition in agriculture. The establishment of bioethanol plants could create employment across multiple sectors, including agriculture, manufacturing, and transportation [52] . Increased demand for bioethanol feedstocks, such as corn stover, can provide an additional revenue stream for farmers, with potential positive effects on rural economies [53] . Furthermore, bioethanol blending could reduce Zambia’s reliance on imported petroleum, thereby easing pressure on foreign currency reserves. The displacement of an estimated 44.5 million liters of gasoline annually could translate into significant foreign exchange savings, with potential implications for national resource allocation [54] .

The successful integration of bioethanol into Zambia’s fuel market may require supportive policies, infrastructure investment, and public awareness initiatives. Studies indicate that countries with well-developed bioethanol programs often implement policy frameworks that incentivize bioethanol production and distribution [55] . The long-term sustainability of bioethanol blending could depend on factors such as feedstock availability, production efficiency, and market competitiveness. Research on second-generation bioethanol derived from agricultural residues suggests additional environmental benefits compared to first-generation bioethanol, indicating potential avenues for further investigation [56] .