This study assesses the bioenergy potential of two types of aquatic biomass found in the Republic of Congo: the green macroalgae Ulva lactuca (UL) and Ledermanniella schlechteri (LS). Their combustion behaviour was assessed using elemental and biochemical analysis, TGA, bomb calorimetry and metal analysis. Their anaerobic digestion behaviour was determined using biochemical methane potential (BMP) tests. The average HHV for LS is 14.1 MJ kg⁻¹, whereas UL is lower (10.5 MJ kg⁻¹). Both biomasses have high ash contents and would be problematic during thermal conversion due to unfavourable ash behaviour. Biochemical analysis indicated high levels of carbohydrate and protein and low levels of lipids and lignin. Although the lipid profile is desirable for biodiesel production, the levels are too low for feasible extraction. High levels of carbohydrates and protein make both biomasses suitable for anaerobic digestion. BMP tests showed that LS and UL have an average of 262 and 161 mL CH₄ gVS⁻¹, respectively. The biodegradability (BI) of LS and UL had an average value of 76.5% and 43.5%, respectively. The analysis indicated that these aquatic biomasses are unsuitable for thermal conversion and lipid extraction; however, conversion through anaerobic digestion is promising.

This study assesses and characterizes six woody biomass (WB) species commonly harvested in the Republic of Congo: Millettia laurentii (WB1), Millettia eetveldeana (WB2), Hymenocardia ulmoides (WB3), Markhamia tomentosa (WB4), Pentaclethra eetveldeana (WB5), and Hymenocardia acida (WB6). Characterization was performed using proximate analysis with a Thermo Gravimetric Analyser (TGA), ultimate analysis with a CHNS Analyser, higher heating value (HHV) determination, metal content analysis by X-ray fluorescence (XRF), and aboveground biomass (AGB) estimation. The proximate analysis results showed that volatile matter varied between 74.6% and 77.3%, while the ultimate analysis indicated that carbon content ranged from 43% to 46%, with low nitrogen content. XRF analysis revealed low levels of heavy metals in all samples. The HHV results, using three models (Dulong’s equation, Friedl, and proximate analysis), showed higher values with Friedl’s method (17.3–18.2 MJ/kg) and proximate analysis (15.26–19.23 MJ/kg) compared to Dulong’s equation (13.9–14.9 MJ/kg). Savannah biomass (WB6) exhibited high AGB (7.28 t), 14.55 t/ha, and carbon stock (7.28 t). Compared to forest biomass, savannah biomass presents a higher potential for bioenergy production. Minimal statistical analysis of wood biomass showed that parameters such as volatile matter (VM), carbon (C), hydrogen (H), and calculated HHV have low variability, suggesting the biomass is relatively homogeneous. However, moisture and nitrogen showed significant standard deviations, indicating variability in storage conditions or sample nature. Statistical analysis of forest biomass estimation revealed different mean values for diameter, AGB (t and t/ha), and carbon stock, with high standard deviations, indicating a heterogeneous forest with both young and mature trees. These analyses and estimates indicate that these WB species are suitable for biofuel and bioenergy production using gasification, pyrolysis, and combustion processes. Among these thermochemical processes, gasification is the most efficient compared to combustion and pyrolysis.

In the context of increasing energy demand and limited access to clean cooking and heating fuels in the Republic of Congo, agricultural and forestry residues represent a promising resource for energy production. This study aims to identify, quantify and assess the energy potential of the residues generated across eight departments of the country. Ten residues were characterized: sugarcane bagasse, peanut shells, corn stalks and cobs, rice husks, cassava stalks and peelings, sawdust, wood chips and wood slabs. Proximate analyses were carried out using a muffle furnace and an oven, while the calorific value was estimated using empirical formulas. Results of the proximate analysis showed that moisture content ranged from 8.80 ± 0.14% to 45.17 ± 1.57%, ash content from 1.00 ± 0.23 to 15.07 ± 0.15%, volatile matter content from 67.86 ± 0.02 to 82.14 ± 0.14% and fixed carbon content from 12.13 ± 0.33 to 19.87 ± 0.37%. The lower calorific value ranged between 14.98 and 18.04 MJ/kg. Approximately 137,921.16 tons of the assessed residues were estimated to be generated in 2025, corresponding to a first-order theoretical energy potential of approximately 1876.78 TJ/year. These findings provide useful evidence for public policies aimed at promoting the sustainable valorization of agricultural, agro-industrial, and forestry residues, diversifying the national energy mix and supporting the development of decentralized bioenergy systems in the Republic of Congo.

In the context of increasing energy demand and limited access to clean cooking and heating fuels in the Republic of Congo, agricultural and forestry residues represent a promising resource for energy production. The aim of this study is to identify, quantify and assess the energy potential of the residues generated across eight departments of the Country. Ten residues were characterized: sugarcane bagasse, peanut shells, corn stalks and cobs, rice husks, cassava stalks and peelings, sawdust, wood chips and wood slabs. Proximate analyses were carried out using a muffle furnace and an oven, while the calorific value was estimated using empirical formulas. Results of proximate analysis showed that moisture content ranged between 8.80 ± 0.14 % and 45.17 ± 1.57 %, ash content from 1.00 ± 0.23 to 15.07 ± 0.15 %, volatile matter content from 67.86 ± 0.02 to 82.14 ± 0.14 % and fixed carbon content from 12.13 ± 0.33 to 19.87 ± 0.37 %. The lower calorific value ranged between 14.98 and 18.04 MJ/kg. Approximately 137 921.16 tonnes of available residues were generated in 2025, representing an estimated energy potential of 1876.78 TJ/year. These residues constitute a significant resource for solid biofuel production and decentralized electricity generation.