Industrial sugar beets to biofuel: Field to fuel production system and cost estimates

Specialized varieties of sugar beets (Beta vulgaris L.) may be an eligible feedstock for advanced biofuel designation under the USA Energy Independence and Security Act of 2007. These non-food industrial beets could double ethanol production per hectare compared to alternative feedstocks. A mixed-integer mathematical programming model was constructed to determine the breakeven price of ethanol produced from industrial beets, and to determine the optimal size and biorefinery location. The model, based on limited field data, evaluates Southern Plains beet production in a 3-year crop rotation, and beet harvest, transportation, and processing. The optimal strategy depends critically on several assumptions including a just-in-time harvest and delivery system that remains to be tested in field trials. Based on a wet beet to ethanol conversion rate of 110 dm³ Mg⁻¹ and capital cost of 128 M$ for a 152 dam³ y⁻¹ biorefinery, the estimated breakeven ethanol price was 507 $ m⁻³. The average breakeven production cost of corn (Zea mays L.) grain ethanol ranged from 430 to 552 $ m⁻³ based on average net corn feedstock cost of 254 and 396 $ m⁻³ in 2014 and 2013, respectively. The estimated net beet ethanol delivered cost of 207 $ m⁻³ was lower than the average net corn feedstock cost of 254–396$ m⁻³ in 2013 and 2014. If for a mature industry, the cost to process beets was equal to the cost to process corn, the beet breakeven ethanol price would be $387 m^-3 (587 $ m⁻³ gasoline equivalent).     

An alkaline direct NaBH4–H2O2 fuel cell with high power density

A high performance alkaline direct borohydride–hydrogen peroxide fuel cell with Pt–Ru catalyzed nickel foam as anode and Pd–Ir catalyzed nickel foam as cathode is reported. The electrodes were prepared by electrodeposition of the catalyst components on nickel foam. Their morphology and composition were analyzed by SEM–EDX. The effects of concentrations of NaBH₄ and H₂O₂ as well as operation temperature on the cell performance were investigated. The cell exhibited an open circuit voltage of about 1.0 V and a peak power density of 198 mW cm⁻² at a current density of 397 mA cm⁻² and a cell voltage of 0.5 V using 0.2 mol dm⁻³ NaBH₄ as fuel and 0.4 mol dm⁻³ H₂O₂ as oxidant operating at room temperature. Electrooxidation of NaBH₄ on Pt–Ru nanoparticles was studied using a rotating disk electrode and complete 8e⁻ oxidation was observed in 2 mol dm⁻³ NaOH solution containing 0.01 mol dm⁻³ NaBH₄.     

Comparison of the effectivities of two-phase and single-phase anaerobic sequencing batch reactors during dairy wastewater treatment

The performances of anaerobic sequencing batch reactors fed with two different substrates were studied. The substrates were raw acid whey and acid whey fermented with Kluyveromyces lactis in order to investigate the suitability of ethanol for biogas production. The organic loading rates (OLRs) during the experiment ranged from 1.6 to 12.8 g COD dm⁻³ d⁻¹ and the corresponding decreasing hydraulic retention times from 40 to 5 days for both reactor systems. The efficiency of each system depended on the OLR: the highest COD removal rate was observed at the lowest OLR applied (about 100% in both systems), and at maximum OLR the COD removal efficiency was 68% for the reactors fed with the raw whey and 80% for those fed with the pre-fermented whey. Under the same high OLR conditions the methane yield was 0.122 dm⁻³ CH₄ g⁻¹ COD_degraded for the anaerobic digesters fed with the untreated whey, and 0.197 dm⁻³ CH₄ g⁻¹ COD_degraded for those fed with the pre-fermented whey. The digesters functioned without pH control. At the maximum OLR the pH in the reactors fed with the raw acid whey was 5.1, while in those fed with the pre-fermented whey it was 7.15.The results demonstrate that the use of the pre-fermented acid whey as substrate for anaerobic digestion without pH control is feasible, especially at high OLR levels. This substrate is preferable to the raw acid whey, because of the ethanol formed as a non-acidic fermentation product of the yeast.     

Assaí – An energy view on an Amazon residue

This paper analyzed the technical and economic feasibility of electricity generation using the residues from the exploitation of Assaí, an Amazonian agrosilvicultural product (Euterpe oleracea, Mart). Assaí biomass characteristics as fuel were reviewed based on available literature and its availability assessed. The profile of a typical industrial processing unit was described. The electricity generation cost for a 1 MW conversion systems, considering 5.5 US$ t⁻¹ biomass price, were evaluated: conventional steam cycle with backpressure turbine (66.97 US$ MWh⁻¹), steam cycle with extraction condensation turbine (92.11 US$ MWh⁻¹), organic Rankine cycle (ORC – 122 US$ MWh⁻¹) and a gasifier/internal combustion engine set (102 US$ MWh⁻¹). Based on financial performance, back-pressure steam turbine was the best option, and gasifier/internal combustion should be further considered due its operation flexibility. For any system, minimal electricity commercialization price for economical feasibility found was 150 US$ MWh⁻¹.     

Thermogalvanic conversion of heat to electricity

A thermogalvanic (nonisothermal) cell was constructed for carrying out power conversion efficiency measurements. The design departed from that of traditional thermogalvanic cells which have largely been used only for studies of open-circuit voltage. The cell was used to obtain temperature coefficients, ∂E/∂T, of the open circuit voltage and power conversion efficiencies, Φ, for an interelectrode temperature difference, ΔT, of 20 K, using various redox couples. The values obtained were the following: Cu²⁺/Cu (1.0 mol dm⁻³), ∂E/∂T = 785 μV K⁻¹; Zn²⁺/Zn (1.0 mol dm⁻³), ∂E/∂T = 790 μV K⁻¹; Fe phen(CN)₄⁻/Fe phen(CN)₄²⁻ (10⁻³ mol dm⁻³), ∂E/∂T = 1046 μV K⁻¹, Φ = 4.17 × 10⁻⁵%; Fe(CN)₆³⁻/Fe(CN)₆⁴⁻ (0.07 mol dm⁻³), ∂E/∂T = 1600 μV K⁻¹, Φ = 1.4 × 10⁻²%. More detailed studies of the latter system when [Fe(CN)₆³⁻] = [Fe(CN)₆⁴⁻] = 0.26 mol dm⁻³ and [KCl] = 0.80 mol dm⁻³, using platinum electrodes, with ΔT = 20 K, gave a current density of 1.45 mA cm⁻² and a power conversion efficiency, Φ, of 2.8 × 10⁻²%. This approaches 0.5% of the maximum theoretical efficiency of a Carnot engine operating across the same temperature difference.     

Use of treated effluent water in ethanol production from cellulose

The bioethanol industry exerts a significant demand on water supplies. Current water consumption rate in corn dry grind ethanol plants is (11–15) dm³ m⁻³ of ethanol produced and (23–38) dm³ m⁻³ for cellulosic ethanol plants. The main goal of this study was to examine the feasibility of use of treated wastewater effluent in place of potable freshwater for cellulosic ethanol production. The effects of using two different types of filtered treated effluent; Bloomington- Normal, IL (Residential type) and Decatur, IL (Industrial/Residential Mix type); on the rate of fermentation and final ethanol yield from a pure cellulosic substrate were evaluated. Characterization analysis of both effluent water samples indicated low concentration of toxic elements. Final ethanol concentrations obtained with Bloomington- Normal and Decatur effluent and with a control treatment using de-ionized water were similar, resulting in 360 g kg⁻¹ (0.36 g g⁻¹), 370 g kg⁻¹ (0.37 g g⁻¹) and 360 g kg⁻¹ (0.36 g g⁻¹), respectively. These findings suggest that with proper characterization studies and under appropriate conditions, the use of treated effluent water in cellulosic ethanol production is feasible.     

Ethanol production from food residues

Food residues were converted to ethanol by simultaneous saccharification with an amylolytic enzyme complex (a mixture of amyloglucosidase, ??-amylase, and protease), and fermentation (SSF) with the yeast, Saccharomyces cerevisiae. About 36 g dm⁻³ of ethanol was obtained from 100 g dm⁻³ food residue in 48 h of fermentation. In the SSF with no nitrogen supplements, 25 g dm⁻³ of ethanol was produced from 100 g dm⁻³ food residues. In addition, none of the nutrient components except yeast extract from the SSF medium were found to affect ethanol production from food residues. This result indicates that food residues could be a good economic bioresource for ethanol production.     

Incorporation of polyaniline into macropores of three-dimensionally ordered macroporous carbon electrode for electrochemical capacitors

Three-dimensionally ordered macroporous (3DOM) carbons having walls composed of mesosized spherical pores were prepared by a colloidal crystal templating method. A composite electrode consisting of bimodal porous carbon and polyaniline (PAn) was prepared by electropolymerization of aniline within the macropores of the bimodal porous carbon. It was found that the deposition of PAn decreased the porosity and specific surface area (SSA) of the electrode. The electrochemical properties of the composite electrode were characterized in a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) containing 1 mol dm⁻³ LiPF₆. The discharge capacity of the carbon–PAn composite electrode was 111 mAh g_carbon–PAn⁻¹ in the potential range of 2.0–4.0 V vs. Li/Li⁺, which corresponded to a volumetric discharge capacity of 53 mAh cm⁻³. Both the double-layer capacity (30 mAh g⁻¹) and the redox capacity of PAn (81 mAh g⁻¹) contributed to the discharge capacity of the composite electrode. The carbon–PAn composite showed good rate capability, and the discharge capacity at a high current density of 6.0 A g⁻¹ was as high as 81 mAh g⁻¹.     

An evaluation of cassava, sweet potato and field corn as potential carbohydrate sources for bioethanol production in Alabama and Maryland

The recent emphasis on corn production to meet the increasing demand for bioethanol has resulted in trepidation regarding the sustainability of the global food supply. To assess the potential of alternative crops as sources of bioethanol production, we grew sweet potato (Ipomoea batatas) and cassava (Manihot esculentum) at locations near Auburn, Alabama and Beltsville, Maryland in order to measure root carbohydrate (starch, sucrose, glucose) and root biomass. Averaged for both locations, sweet potato yielded the highest concentration of root carbohydrate (ca 80%), primarily in the form of starch (ca 50%) and sucrose (ca 30%); whereas cassava had root carbohydrate concentrations of (ca 55%), almost entirely as starch. For sweet potato, overall carbohydrate production was 9.4 and 12.7 Mg ha⁻¹ for the Alabama and Maryland sites, respectively. For cassava, carbohydrate production in Maryland was poor, yielding only 2.9 Mg ha⁻¹. However, in Alabama, carbohydrate production from cassava averaged 10 Mg ha⁻¹. Relative to carbohydrate production from corn in each location, sweet potato and cassava yielded approximately 1.5× and 1.6× as much carbohydrate as corn in Alabama; 2.3× and 0.5× for the Maryland site. If economical harvesting and processing techniques could be developed, these data suggest that sweet potato in Maryland, and sweet potato and cassava in Alabama, have greater potential as ethanol sources than existing corn systems, and as such, could be used to replace or offset corn as a source of biofuels.     

The economic feasibility of sugar beet biofuel production in central North Dakota

This study examines the financial feasibility of producing ethanol biofuel from sugar beets in central North Dakota. Under the Energy Independence and Security Act (EISA) of 2007, biofuel from sugar beets uniquely qualifies as an “advanced biofuel”. EISA mandates production of 21 billion gallons of advanced biofuels annually by 2022. A stochastic simulation financial model was calibrated with irrigated sugar beet data from central North Dakota to determine economic feasibility and risks of production for 0.038 hm³y⁻¹ (or 10 MGY (Million Gallon per Year) and 0.076 hm³y⁻¹ (or 20 MGY) ethanol plants. Study results indicate that feedstock costs, which include sugar beets and beet molasses, account for more than 70 percent of total production expenses. The estimated breakeven ethanol price for the 0.076 hm³y⁻¹ plant is $400 m⁻³ ($1.52 per gallon) and $450 m⁻³ ($1.71 per gallon) for the 0.038 hm³y⁻¹ plant. Breakeven prices for feedstocks are also estimated and show that the 0.076 hm³y⁻¹ plant can tolerate greater ethanol and feedstock price risks than the 0.038 hm³y⁻¹ plant. Our results also show that one of the most important factors that affect investment success is the price of ethanol. At an ethanol price of $484.21 m⁻³ ($1.84 per gallon), and assuming other factors remain unchanged, the estimated net present value (NPV) for the 0.076 hm³y⁻¹ plant is $41.54 million. By comparison, the estimated NPV for the 0.038 hm³y⁻¹ plant is only $8.30 million. Other factors such as changes in prices of co-products and utilities have a relatively minor effect on investment viability.     

Overview analysis of bioenergy from livestock manure management in Taiwan

The emissions of greenhouse gases (GHGs) from the livestock manure are becoming significant energy and environmental issues in Taiwan. However, the waste management (i.e., anaerobic digestion) can produce the biogas associated with its composition mostly consisting of methane (CH₄), which is now considered as a renewable energy with emphasis on electricity generation and other energy uses. The objective of this paper was to present an overview analysis of biogas-to-bioenergy in Taiwan, which included five elements: current status of biogas sources and their energy utilizations, potential of biogas (methane) generation from livestock manure management, governmental regulations and policies for promoting biogas, benefits of GHGs (i.e., methane) emission reduction, and research and development status of utilizing livestock manure for biofuel production. In the study, using the livestock population data surveyed by the Council of Agriculture (Taiwan) and the emission factors recommended by the Intergovernmental Panel on Climate Change (IPCC), the potential of methane generation from livestock manure management in Taiwan during the period of 1995–2007 has been estimated to range from 36 to 56 Gg year⁻¹, indicating that the biogas (methane) from swine and dairy cattle is abundant. Based on the characteristics of swine manure, the maximum potential of methane generation could reach to around 400 Gg year⁻¹. With a practical basis of the total swine population (around 4300 thousand heads) from the farm scale of over 1000 heads, a preliminary analysis showed the following benefits: methane reduction of 21.5 Gg year⁻¹, electricity generation of 7.2 × 10⁷ kW-h year⁻¹, equivalent electricity charge saving of 7.2 × 10⁶ US$ year⁻¹, and equivalent carbon dioxide mitigation of 500 Gg year⁻¹.     

Comparative study of bio-ethanol production from mahula (Madhuca latifolia L.) flowers by Saccharomyces cerevisiae cells immobilized in agar agar and Ca-alginate matrices

Batch fermentation of mahula (Madhuca latifolia L., a tree commonly found in tropical rain forest) flowers was carried out using immobilized cells (in agar agar and calcium alginate) and free cells of Saccharomyces cerevisiae. The ethanol yields were 151.2, 154.5 and 149.1 g kg⁻¹ flowers using immobilized (in agar agar and calcium alginate) and free cells, respectively. Cell entrapment in calcium alginate was found to be marginally superior to those in agar agar (2.2% more) as well as over free cell (3.5% more) as regard to ethanol yield from mahula flowers is concerned. Further, the immobilized cells were physiologically active at least for three cycles [150.6, 148.5 and 146.5 g kg⁻¹ (agar agar) and 152.8, 151.5 and 149.5 g kg⁻¹ flowers (calcium alginate) for first, second and third cycle, respectively] of ethanol fermentation without apparently lowering the productivity. Mahula flowers, a renewable, non-food-grade cheap carbohydrate substrate from non-agricultural environment such as forest can serve as an alternative to food grade sugar/starchy crops such as maize, sugarcane for bio-ethanol production.     

Techno-economic analysis of using corn stover to supply heat and power to a corn ethanol plant – Part 2: Cost of heat and power generation systems

This paper presents a techno-economic analysis of corn stover fired process heating (PH) and the combined heat and power (CHP) generation systems for a typical corn ethanol plant (ethanol production capacity of 170 dam³). Discounted cash flow method was used to estimate both the capital and operating costs of each system and compared with the existing natural gas fired heating system. Environmental impact assessment of using corn stover, coal and natural gas in the heat and/or power generation systems was also evaluated. Coal fired process heating (PH) system had the lowest annual operating cost due to the low fuel cost, but had the highest environmental and human toxicity impacts. The proposed combined heat and power (CHP) generation system required about 137 Gg of corn stover to generate 9.5 MW of electricity and 52.3 MW of process heat with an overall CHP efficiency of 83.3%. Stover fired CHP system would generate an annual savings of 3.6 M$ with an payback period of 6 y. Economics of the coal fired CHP system was very attractive compared to the stover fired CHP system due to lower fuel cost. But the greenhouse gas emissions per Mg of fuel for the coal fired CHP system was 32 times higher than that of stover fired CHP system. Corn stover fired heat and power generation system for a corn ethanol plant can improve the net energy balance and add environmental benefits to the corn to ethanol biorefinery.     

Solar chemical reactor technology for industrial production of lime

We developed the solar chemical reactor technology to effect the endothermic calcination reaction CaCO₃(s) → CaO(s) + CO₂(g) at 1200–1400 K. The indirect heating 10 kW_th multi-tube rotary kiln prototype processed 1–5 mm limestone particles, producing high purity lime that is not contaminated with combustion by-products. The quality of the solar produced quicklime meets highest industrial standards in terms of reactivity (low, medium, and high) and degree of calcination (exceeding 98%). The reactor’s efficiency, defined as the enthalpy of the calcination reaction at ambient temperature (3184 kJ kg⁻¹) divided by the solar energy input, reached 30–35% for quicklime production rates up to 4 kg h⁻¹. The solar lime reactor prototype operated reliably for more than 100 h at solar flux inputs of about 2000 kW m⁻², withstanding the thermal shocks that occur in solar high temperature applications. By substituting concentrated solar energy for fossil fuels as the source of process heat, one can reduce by 20% the CO₂ emissions in a state-of-the-art lime plant and by 40% in a conventional cement plant. The cost of solar lime produced in a 20 MW_th industrial solar calcination plant is estimated in the range 131–158 $/t, i.e. about 2–3 times the current selling price of conventional lime.     

Energy self-sufficient production of bioethanol from a mixture of hemp straw and triticale seeds: Life-cycle analysis

Industrial hemp shows exceptional potential for cellulosic ethanol production, especially regarding yields per hectare, costs and environmental impact. Additionally, co-products, such as high-value food-grade oil, increase the value of this plant. In this work, hemp straw was steam-exploded for 45 min at 155 °C and hydrolysed with a cellulase/xylanase mixture. Up to 0.79 g g⁻¹ of cellulose was degraded and subsequent simultaneous-saccharification-and-fermentation with added triticale grist resulted in >0.90 g g⁻¹ fermentation of cellulose. Hemp straw is very suitable, as it contains 0.63 g g⁻¹ of cellulose and only 0.142 g g⁻¹ of hemicellulose.A 2000 m³ a⁻¹ ethanol biorefinery requires a land use of 3 km² each for hemp and for triticale. A total of 2630 kg ethanol and 150 kg hemp oil can be gained from 1 ha. Slurry and triticale straw serve as raw material for the biogas fermenter or as animal feed. Biogas supplies thermal and electric energy in combined heat and power. Ethanol will remain at 0.66 € dm⁻³ based on market prices. In addition, data have been calculated for market prices plus and minus 30% market prices (0.51–0.81 € dm⁻³). Carbon dioxide (CO₂) abatement for ethanol achieves 121 g MJ⁻¹ CO_2eq for a combined ethanol/biogas plant. The CO₂ abatement costs vary from 38 € to 262 € t⁻¹ CO_2eq.     

Process for the recycling of alkaline and zinc–carbon spent batteries

In this paper a recycling process for the recovery of zinc and manganese from spent alkaline and zinc–carbon batteries is proposed. Laboratory tests are performed to obtain a purified pregnant solution from which metallic zinc (purity 99.6%) can be recovered by electrolysis; manganese is recovered as a mixture of oxides by roasting of solid residue coming from the leaching stage. Nearly 99% of zinc and 20% of manganese are extracted after 3 h, at 80 °C with 10% w/v pulp density and 1.5 M sulphuric acid concentration. The leach liquor is purified by a selective precipitation of iron, whereas metallic impurities, such as copper, nickel and cadmium are removed by cementation with zinc powder. The solid residue of leaching is roasted for 30 min at 900 °C, removing graphite completely and obtaining a mixture of Mn₃O₄ and Mn₂O₃ with 70% grade of Mn. After that a technical-economic assessment is carried out for a recycling plant with a feed capacity of 5000 t y⁻¹ of only alkaline and zinc–carbon batteries. This analysis shows the economic feasibility of that plant, supposing a battery price surcharge of 0.5 € kg⁻¹, with a return on investment of 34.5%, gross margin of 35.8% and around 3 years payback time.     

High rate low solids methane fermentation of sorghum, corn and cellulose

Sorghum, sorghum/alpha-cellulose mixture, and corn were anaerobically digested at 55°C at effluent solids contents of 8–12% total solids (TS), using trace nutrient supplementation. Volatile solids (VS) loading rates at much higher levels than conventional maxima were maintained without volatile fatty acid (VFA) accumulation. Semi-continuously fed digesters with organic loading rates (OLR) up to 12 gVS kg⁻¹ d⁻¹ produced methane at rates up to 3.3 L kg⁻¹d⁻¹. Continuous feeding of corn at an OLR of 18 gVS kg⁻¹ d⁻¹ resulted in a methane production rate of 5.4 L kg⁻¹d⁻¹. VS removal efficiencies at maximum OLRs were 60% (sorghum) and 67% (corn). At an OLR of 4 gVS kg⁻¹ d⁻¹ sorghum alone as a feedstock led to excess ammonia-N accumulation. Excess ammonia did not accumulate at sorghum loading rates of 8 and 12 gVS kg⁻¹ d⁻¹ nor with a sorghum/alpha-cellulose mix loaded at 8 gVS kg⁻¹ d⁻¹. Instantaneous gas production rates were directly related to feedstock cell soluble content, with peak instantaneous biogas production rates from corn (OLR of 8 gVS kg⁻¹ d⁻¹ approaching 25 L kg⁻¹ d⁻¹ following a three-day feeding.     

Potential bioethanol and biogas production using lignocellulosic biomass from winter rye, oilseed rape and faba bean

To meet the increasing need for bioenergy several raw materials have to be considered for the production of e.g. bioethanol and biogas. In this study, three lignocellulosic raw materials were studied, i.e. (1) winter rye straw (Secale cereale L), (2) oilseed rape straw (Brassica napus L.) and (3) faba bean straw (Viciafaba L.). Their composition with regard to cellulose, hemicellulose, lignin, extractives and ash was evaluated, as well as their potential as raw materials for ethanol and biogas production. The materials were pretreated by wet oxidation using parameters previously found to be optimal for pretreatment of corn stover (195 °C, 15 min, 2 g l⁻¹ Na₂CO₃ and 12 bar oxygen). It was shown that pretreatment was necessary for ethanol production from all raw materials and gave increased biogas yield from winter rye straw. Neither biogas productivity nor yield from oilseed rape straw or faba bean straw was significantly affected by pretreatment. Ethanol was produced by the yeast Saccharomyces cerevisiae during simultaneous enzymatic hydrolysis of the solid material after wet oxidation with yields of 66%, 70% and 52% of theoretical for winter rye, oilseed rape and faba bean straw, respectively. Methane was produced with yields of 0.36, 0.42 and 0.44 l g⁻¹ volatile solids for winter rye, oilseed rape and faba bean straw, respectively, without pretreatment of the materials. However, biogas productivity was low and it took over 50 days to reach the final yield. It could be concluded that all three materials are possible raw materials for either biogas or ethanol production; however, improvement of biogas productivity or ethanol yield is necessary before an economical process can be achieved.     

Evaluation of hydrogen and methanol fuel cell performance of sulfonated diels alder poly(phenylene) membranes

Hydrogen fuel cell performance of sulfonated diels alder poly(phenylene) (SDAPP) with IECs ≥ 1.8 meq g⁻¹ is comparable to Nafion 212 under fully humidified conditions at 80 °C. However, as relative humidity is reduced, performance loss is substantial for SDAPP when compared to Nafion 212. This loss can be attributed to the large drop in proton conductivity in SDAPP as relative humidity is reduced; the proton conductivity of SDAPP with an IEC of 2.3 meq g⁻¹ dropped from 0.117 S cm⁻¹ to 0.001 S cm⁻¹ as the relative humidity was reduced from 100% to 25% at 80 °C. Methanol fuel cell experiments using 3 M methanol result in a 60 mV performance improvement at 25 mA cm⁻² when using SDAPP with an IEC of 1.2 meq g⁻¹ instead of Nafion 212. This improvement is due to lower methanol permeability of SDAPP (1.4 meq g⁻¹) over Nafion 212, with SDAPP films having methanol permeabilities less than 25% of Nafion 212.     

Optimization of alkaline pretreatment on corn stover for enhanced production of 1.3-propanediol and 2,3-butanediol by Klebsiella pneumoniae AJ4

Corn stover is one of the most promising lignocellulosic biomass that can be utilized for producing 1,3-propanediol and 2,3-butanediol. The pretreatment and enzymatic hydrolysis steps are essential for the bioconversion of lignocellulosic biomass to diols. For optimizing the pretreatment step, temperature, time, and NaOH concentration were evaluated based on total sugar recovery. Enzymatic hydrolysis for cellulose and hemicellulose were investigated at different solid-to-liquid ratios. The optimum conditions were found to be alkaline pretreatment with 0.25 mol dm⁻³ NaOH for 1 h at 60 °C followed by enzymatic hydrolysis at 50 °C for 48 h, with a solid slurry concentration of 100 g dm⁻³. Under these conditions, conversion rates of 92.55% and 78.82% were obtained from glucan and xylan, respectively. Diol production from fermentable sugars was 14.8 g dm⁻³, with a conversion yield and productivity of 0.46 g g⁻¹, and 0.98 g dm⁻³ h⁻¹, respectively. Our results are similar for diol production obtained using pure sugars under the same conditions. Therefore, mild alkaline pretreatment of corn stover facilitates delignification, significantly improving the rate of enzymatic saccharification and sugar recovery.