The co-hydrothermal carbonization of biomasses has shown many advantages on charcoal yield, carbonization degree, thermal-stability of hydrocar and energy recovered. The goal of this study is to investigate the effect of co-combustion of cattle manure and sawdust on energy recovered. The results show that ash content ranged between 10.38%–20.00%, indicating that the proportion of each variable influences energy recovered. The optimum is obtained at 51% cattle manure and 49% sawdust revealing 37% thermal efficiency and 3.9 kW fire power. These values are higher compared to cattle manure individually which gives values of 30% and 2.3 kW respectively for thermal efficiency and fire power. Thus, the mixture of biomasses enhances energy recovered both in combustion and hydrothermal carbonization. Volatile matter is lower in mixture predicting that the flue gas releases is lower during combustion. Fixed carbon is higher in mixture predicting that energy recovered increases during the combustion of mixture than cattle manure individually. Higher Carbon content was noticed in mixture than cattle manure indicating that the incorporation of sawdust enhances heating value. The incorporation of sawdust in cattle manure can also enhance energy recovered and is more suitable for domestic and industrial application.

1. IEA. Africa energy outlook: A focus on energy prospects in sub-Saharan Africa. World Energy Outlook 2021. International Energy Agency, Paris; 2021. doi: 10.1787/weo-2021-en

2. Ouedraogo NS. Africa energy future: Alternative scenarios and their implications for sustainable development strategies. Energy Policy. 2017; 106: 457-471. doi: 10.1016/j.enpol.2017.03.021

3. Deichmann U, Meisner C, Murray S, Wheeler D. The economics of renewable energy expansion in rural Sub-Saharan Africa. Energy Policy. 2011; 39: 215-227.

4. Brunet C, Savadogo O, Baptiste P, Bouchard MA. Shedding some light on photovoltaic solar energy in Africa—A literature review. Renew Sustain Energy Rev. 2018; 96: 325-342. doi: 10.1016/j.rser.2018.08.004

5. Mohammed YS, Mustafa MW, Bashir N. Status of renewable energy consumption and developmental challenges in Sub-Sahara Africa. Renewable and Sustainable Energy Reviews. 2013; 27: 453-463. doi: 10.1016/j.rser.2013.06.044

6. Samomssa I, Jiokap YN, Kamga R. Energy potential of waste derived from some food crop products in the northern part of Cameroon. Int J Energy Power Eng. 2015; 4: 342-352. doi: 10.11648/j. ijepe.20150406.13

7. IRENA. Africa Power Sector: Planning and Prospects for Renewable Energy. Abu Dhabi/Bonn: IRENA; 2015.

8. Sharma S, Kundu A, Basu S, et al. Sustainable environmental management and related biofuel technologies. Journal of Environmental Management. 2020; 273: 111096. doi: 10.1016/j.jenvman.2020.111096

9. Hoang AT. Experimental study on spray and emission characteristics of a diesel engine fueled with preheated bio-oils and diesel fuel. Energy. 2019; 171: 795-808.

10. Atarod P, Khlaife E, Aghbashlo M, et al. Soft computing-based modeling and emission control/reduction of a diesel engine fueled with carbon nanoparticle-dosed water/diesel emulsion fuel. J. Hazard Mater. 2020; 124369.

11. Cao DN, Hoang AT, Luu HQ, et al. Effects of injection pressure on the NOx and PM emission control of diesel engine: a review under the aspect of PCCI combustion condition. Energy Sources. Part A Recover. Util. Environ. Eff. 2020; 1-18.

12. Stanislav V, Vassilev C, Vassileva G, Vassil SV. Advantages and disadvantages of composition and properties of biomass in comparison with coal: An overview. Fuel. 2015; 158: 330-350. doi: 10.1016/j.fuel.2015.05.050

13. Anh TH, Atabani E, Nizetic S, et al. Acid-based lignocellulosic biomass biorefinery for bioenergy production: Advantages, application constraints, and perspectives. Journal of Environmental Management. 2021; 296: 113194. doi: 10.1016/j.jenvman.2021.113194

14. Jaramillo P, Muller NZ. Air pollution emissions and damages from energy production in the U.S.: 2002–2011. Energy Policy. 2016; 90: 202-211. doi: 10.1016/j.enpol.2015.12.035

15. Hasanbeigi A, Lynn P. A technical review of emerging technologies for energy and water efficiency and pollution reduction in the textile industry. J. Clean. Prod. 2015; 95: 30-44. doi: 10.1016/j.jclepro.2015.02.079

16. Li LL, Lou JL, Tseng ML, et al. A hybrid dynamic economic environmental dispatch model for balancing operating costs and pollutant emissions in renewable energy: A novel improved mayfly algorithm. Expert Systems with Applications. 2022; 203: 117411. doi: 10.1016/j.eswa.2022.117411

17. Chia SR, Ong HC, Chew KW, et al. Sustainable approaches for algae utilisation in bioenergy production. Renewable Energy. 2018; 129: 838-852. doi: 10.1016/j.renene.2017.04.001

18. Mahmood N, Zhaohua W, Nazia Y, et al. How to bend down the environmental Kuznets curve: the significance of biomass energy. Environ. Sci. Pollut. Res. 2019; 26: 21598-21608. doi: 10.1007/s11356-019-05442-1

19. Parthasarathy P, Narayanan SK. Effect of hydrothermal carbonization reaction parameters on. Environ. Prog. Sustain. Energy. 2014; 33(3): 676-680.

20. Samomssa I, Henriette AZ, Boukar H, et al. Compositional characteristics and theoretical energy potential of animal droppings from Adamawa region of Cameroon. Biomass Convers. Biorefin. 2022. doi: 10.1007/s13399-022-03320-4

21. Azevedo A, Franccesca F, Mateus-da S, et al. Life cycle assessment of bioethanol production from cattle manure. J. Clean. Prod. 2017; 162: 1021-1030. doi: 10.1016/j.jclepro.2017.06.141

22. Lee D, Jun HY, Sungyup J, et al. Valorization of animal manure: A case study of bioethanol production from horse manure. Chem. Eng. J. 2021; 403: 126345. doi: 10.1016/j.cej.2020.126343

23. Hafid HS, Rahman NAA, Shah UKM, et al. Feasibility of using kitchen waste as future substrate for bioethanol production: A review. Renewable and Sustainable Energy Reviews. 2017; 74: 671-686. doi: 10.1016/j.rser.2017.02.071

24. Samomssa I, Jiokap YN, Tsamo C, et al. Inluence of physico-chemical parameters on fuel briquettes properties formulated with mixture of biomasses. J Environ Sci Pollut Res. 2019; 5(2): 338-341. doi: 10.30799/jesps.165.19050202

25. Samomssa I, Nono YJ, Cârâc G, et al. Optimization of fuel briquette production from cassava peels, plantain peels and corn cobs. Journal of Material Cycles and Waste Management. 2021; 23(5): 1905-1917. doi: 10.1007/s10163-021-01260-1

26. Leng L, Huang H. An overview of the effect of pyrolysis process parameters on biochar stability. Bioresource Technology. 2018; 270: 627-642. doi: 10.1016/j.biortech.2018.09.030

27. Kenney KL, Smith WA, Gresham GL, et al. Understanding biomass feedstock variability. Biofuels. 2013; 4(1): 111-127. doi: 10.4155/bfs.12.83

28. Li Y, Liu H, Xiao K, et al. Correlations between the physicochemical properties of hydrochar and specific components of waste lettuce: Influence of moisture, carbohydrates, proteins and lipids. Bioresource Technology. 2019; 272: 482-488. doi: 10.1016/j.biortech.2018.10.066

29. Wang T, Si B, Gong Z, et al. Co-hydrothermal carbonization of food waste-woody sawdust blend: Interaction effects on the hydrochar properties and nutrients characteristics. Bioresource Technology. 2020; 316: 123900. doi: 10.1016/j.biortech.2020.123900

30. Bardhan M, Novera TM, Tabassum M, et al. Co-hydrothermal carbonization of different feedstocks to hydrochar as potential energy for the future world: A review. Journal of Cleaner Production. 2021; 298: 126734. doi: 10.1016/j.jclepro.2021.126734

31. Leng L, Yang L, Chen J, et al. A review on pyrolysis of protein-rich biomass: Nitrogen transformation. Bioresource Technology. 2020; 315: 123801. doi: 10.1016/j.biortech.2020.123801

32. Wu Q, Yu S, Hao N, et al. Characterization of products from hydrothermal carbonization of pine. Bioresource Technology. 2017; 244: 78-83. doi: 10.1016/j.biortech.2017.07.138

33. Hassana B, Mbawala A, Ngassoum M, Ibrahima A. Investigation of some biomasses availability for conversion in biochar: Case of Ngaoundere (Cameroonian). Int. J. Sci. Technol. 2019; 6: 597-609.

34. Tchouanti NB, Onguene MP, Ahmed A, Ruben M. Effect of particle size on syngas production using sawdust of Cameroonian Triplochiton scleroxylon. Sci. Afr. 2019; 6: e00182. doi: 10.1016/j.sciaf.2019.e00182

35. ASTM Standards. Standard test method moisture analysis of particulate wood. Fuels. 2006 ; 1871–1882.

36. ASTM Standards. Standard test method for ash in biomass. Fuels. 2007 ; 1755–1761.

37. ASTM Standards. Standard test method for volatile matter in the analysis of particulate wood. Fuels. 2006 872–882.

38. Torgrip RJO, Fernández-Cano V. Rapid X-ray based determination of moisture-, ash content and heating value of three biofuel assortments. Biomass and Bioenergy. 2017; 98: 161-171. doi: 10.1016/j.biombioe.2017.01.005

39. Ormaechea P, Castrillón L, Suárez-Peña B, et al. Enhancement of biogas production from cattle manure pretreated and/or co-digested at pilot-plant scale. Characterization by SEM. Renewable Energy. 2018; 126: 897-904. doi: 10.1016/j.renene.2018.04.022

40. Tsai WT, Liu SC. Thermochemical characterization of cattle manure relevant to its energy conversion and environmental implications. Biomass Conversion and Biorefinery. 2015; 6(1): 71-77. doi: 10.1007/s13399-015-0165-7

41. Muhammad D, Naqvi M, Usman F, Naqvi S. Characterization of South Asian agricultural residues for potential utilization in future energy mix. Energy Procedia. 2015; 75: 2974-2980. doi: 10.1016/j.egypro.2015.07.604

42. Jiang C, Lin Q, Wang C, et al. Experimental study of the ignition and combustion characteristics of cattle manure under diferent environmental conditions. Energy. 2020; 197: 117143. doi: 10.1016/j.energy.2020.177143