BIOMASS ENERGY POTENTIAL IN RURAL COMMUNITIES
4. CONVERSION OF BIOMASS TO BIOENERGY
4.2 SIMULATION CALCULATION
170 Table 2 – Number of vegetables in the settlement Estrela da Ilha, 2016.
Type of vegetables Number of plants (hectare) Waste (ton.year-1)
Corn 78.26 391.30 permanent crops and annual crops with an annual production of 1,695.53 tonnes of waste.
4.2 SIMULATION CALCULATION
In the case of the technology proposed by this study, the software calculates the biogas production according to the quantity of each type of material to be processed in the biodigester.
Table 3 shows the biomass conversion in biogas calculated by the software, with the dry matter indices (%), biogas production factor (m³.kg-1), annual biogas production (m³) and methane concentration (%).
To estimate the amount of residues produced daily by animals, the study was based on data provided by Sganzerla (1983), Colatto et al. (2011) and Kunz et al. (2006). All indicate the amount of 10 kg of manure by cattle, 2.25 kg by pigs and 0.18 kg by birds.
Table 3 – Estimated total biogas production in the settlement.
Unity
171 The total biogas value is 156,571 m³.year-1 and the methane concentration in the compound is 58.8%. The methane is the gas responsible for the quality of the compound, in the literature, 60-80% is ideal for the proper functioning of the motor generator, otherwise loses efficiency in the production of electric energy.
With the calculated value of the biogas, Table 4 contemplates all the information used by the software, with its respective steps. Information on the biodigestor such as sizing, model and costs was made available by the company RECOLAST through a consultancy for academic purposes and, in relation to the information on the motor generator was made available by the company ER-BR also through a consultancy for academic purposes, both are conceptualized in the market
Table 4 – Main parameters used by software RETScreen.
RETScreen Main parameters
User defined 3% of the initial costs
Periodic costs
Reset the motogenerator R$ 80.000,00 every 7 years
172 When analyzing the feasibility of setting up a power plant with the use of available biomass in the Estrela da Ilha rural settlement, the RETScreen software made it possible to visualize a scenario with the costs of the implementation, operation and maintenance, replacement of equipment, generation revenues the financial viability of the entire project.
The project was estimated for a period of 20 years, with an initial cost of £25,000.00 (motogenerator, biodigestor and construction of the shelter of the biomass pool and storage), annual costs with operation and maintenance of £950.00 and £2,300.00 of debt for a period of 15 years and cost with replacement of the motor generator of £16,500.00 every seven years and the canvas of the biodigestor of £4,700.00 every 11 years.
With this system, an electric power production of 399 MWh.year-1 is estimated at a cost of £48 per MWh. Revenue from the production of electric energy was £19,250.00 with its export to the grid, with a GHG emission reduction of 17 tCO2.year-1 (equivalent to a reduction of 3.1 vehicles).
Through the production of energy, the settlement can be framed in the shared generation, that is to say, it is characterized by the meeting of consumers within the same concession area, where there is a consumer unit with microgeneration or distributed mini generation and the surplus energy is compensated, according to with RN687/2015 provided by ANEEL. By estimating and simulating the potential of the settlement to generate electricity, residents can organize themselves to deploy biodigesters strategically for access and benefit to all.
Regarding financial feasibility, the project obtained a return on equity in seven months, ie, initial investment cost would be amortized in this period. The internal rate of return on equity was 185% and net present value in the amount of £150,000.00 and the cost-benefit ratio of 17.7.
The cost of electric energy consumption in the entire settlement was estimated by the simulator on the site of ELEKTRO (Electric Power utility of São Paulo State) for the month of September 2018 in the amount of £79,000.00 (taxes included). Through revenue from energy production, it can achieve a 24.38% reduction in energy costs throughout the settlement
In conclusion, according to the software application analysis, the implementation of the power generation system in the Estrela da Ilha rural settlement proved to be efficient with the production of electricity through the use of available biomass, with a recovery of initial
173 investments within a period of seven months from own resources. However, it is worth mentioning that the costs of transporting and collecting the biomass to the proposed place for the installation of the power plant were not accounted for.
Finally, in addition to simulating the energy potential of the Estrela do Ilha rural settlement, the study allows creating new scenarios with the planting of energy crops, in order to obtain an increase in bioenergy production of the place through the use of energy mapping, optimizing the area existing.
An example is the planting of elephant grass as an energy crop, destined for the production of biogas. Elephant grass produces 49.75 t.ha.-1.yr-1 dry matter. If you consider only 10% of the pasture land in the Ilha da Estrela settlement, it equals 189.24 hectares, it will produce 9,414.69 tons.yr-1 (NEIVA, 2016). When simulating this biomass in the conversion to biogas, it is estimated a production of 1,694,644 m³. This volume represents more than 10 times the value of biogas production with available biomass.
5. CONCLUSIONS
Rural communities can develop a sustainable model, as in the Estrela da Ilha rural settlement case, from shared generation as stated in the NR 867/2015 from ANEEL. Energy production can be increased from energy crops without affecting current activities. The RenovaBio program which considers purification and commercialization of biomethane as biofuel can also be followed.
Initial costs with the plant's implementation can be a challenge, especially for residents of the Estrela da Ilha rural settlement due to their low average income. Governmental support along with private investors is the key to solve this drawback.
Investors can benefit from the reduction of electricity grid costs and the trade of carbon credits and CBios by the new Brazilian RenovaBio program for biofuels.
Acknowledgments
The authors would like to thank Capes for the funding this research, COATER and the Estrela da Ilha rural settlement residents for providing information and help to this work.
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