**5. Conclusions**

Biomass projects are an interesting alternative to fossil fuels where resources are widely available. Due to its carbon-neutral condition and low price, biomass boilers are having an increasing presence in international markets. According to the Law for the Use of Renewable Energies and the Financing of Energy Transition, Mexico's goal for 2024 is to generate 35% of its energy from non-fossil sources.

Zapote mamey is one of the most widely grown fruits in Mexico, with an annual production of 17,515 t. Zapote industry waste could be used to generate power and reduce CO2 emissions; while the CO2 emissions of LPG are 0.254 kg/kWh, the zapote seed emissions will be theoretically 0. Replacing a 200 kW LPG boiler with a biomass boiler fed with dry zapote seeds in the heavy chemistry laboratory of the Faculty of Engineering of the University of Veracruz in Mexico would mean a reduction in CO2 emissions of 60,960.00 kg/year.

The use of zapote seed as a biofuel has important advantages in the fight against climate change:


Comparing the annual costs of these two sources of energy, the amount saved was predicted to be \$US7,819.79, which means an annual saving of 53.19%. The total investment of the project was estimated to be \$US67,530.48. According to financial results, the project was predicted to be attractive, with its financial variables showing a predicted IRR of 7%, a payback period of 9.8 years, and a B/C ratio of 1.13.

A sensitivity or what-if analysis was carried out because the price and quantity of zapote seed are sensitive to changes. In this case, the project can be accepted if the maximum quantity required increases to 79,281.19 kg but the price decreases 25% (to 0.081 USD), or the maximum price increases 25% to 0.135 USD and the quantity decreases 25% (to 47,568.71 kg).

Regarding policy implications, this study shows that there is a market opportunity for small producers and overall increases in production, which necessitates an adequate credit policy for this sector, including low interest rates, especially during the first few years, as well as flexibility in the terms and forms of payment.

These results pave the way toward the utilization of zapote seed as a solid biofuel, contribute to achieving Mexico's energy goal for 2024, and promote sustainability in universities.

One of the main limitations of this study was the humidity of the zapote seeds. In future work, the possibility of designing dryers for these seeds, built in an environmentally sustainable way, will be studied.

**Author Contributions:** Conceptualization, M.-A.P.-M., Q.H.-E., F.R.-M., and A.-J.P.-M.; methodology, M.-A.P.-M., Q.H.-E., F.R.-M., and A.-J.P.-M.; formal analysis, M.-A.P.-M., Q.H.-E., F.R.-M., and A.-J.P.-M.; investigation, M.-A.P.-M., Q.H.-E., F.R.-M., and A.-J.P.-M.; resources, M.-A.P.-M., Q.H.-E., F.R.-M., and A.-J.P.-M.; writing—original draft preparation, M.-A.P.-M., Q.H.-E., F.R.-M., and A.-J.P.-M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** The authors thank MS. Florentino Sanchez Padilla for his support in obtaining the university laboratory data.

**Conflicts of Interest:** The authors declare no conflict of interest.
