## 4 Conclusions  
This research work aimed at performing a techno-economic feasibility assessment for applying the gasification technology in the agrifood industry. The main findings are summarized below:  
1. Gasification is already a mature and developed technology in some countries such as India, China and the USA. However, its penetration in the Spanish market is negligible or very incipient. The residues from the olive oil and almond industries with potential use as feedstock in the gasification process are the following: exhausted olive pomace, olive pit, olive tree pruning, almond shell, almond hull and almond tree pruning.
2. A small-scale gasification plant was installed for power generation and biochar production using exhausted olive pomace pellets as feedstock. The plant was capable of generating 10-12 kW of rated electric power with an average biomass consumption of 13.3 kg/h. Most of the operating parameters have improved compared to those reported by the manufacturer, leading to a lower feedstock consumption and a higher net electrical efficiency (\(\eta_{e}=17.8\%\)).
3. In addition to the electrical energy generated for self-consumption, the gasification plant produces two additional outputs. One of them is thermal energy in the form of hot water and combustion gases from the engine. Another by-product of gasification is biochar, an extremely porous activated carbon that can absorb water including dissolved nutrients up to five times its own weight when deposited in agricultural soil. Additionally, it has a high cation exchange capacity, avoiding the leaching of mineral nutrients and ensuring greater availability of them in the soil. It also benefits microbial life and increases the potential of microorganisms and roots. Its sale price in international markets ranges between \(\copyright\)150-200/t.
4. Finally, profitability analysis of the gasification technology for a real olive oil mill in Spain was developed. For an initial investment of approximately \(\copyright\)200,000, the payback period is 5-9 years. This technology generates direct employment (operation and maintenance work) and about 10-15 indirect jobs during the installation phase that are technical in nature.  
The results of this research work demonstrate a feasible and attractive possibility for the Spanish agri-food sector to invest in energy efficiency through waste gasification, improving environmental and economic sustainability, diversifying into new business models and promoting a circular economy.  
conceptualization, R.A. and D.V.; methodology, R.A. and D.V.; validation, F.J., R.A. and D.V.; investigation, R.A., D.V. and J.P.T.; writing--original draft preparation, R.A. and D.A.L.-G.; writing--review and editing, R.A., D.V., D.A.L.-G. and J.P.T.; supervision, F.J.; project administration, D.V.; funding acquisition, D.V. and F.J. All authors have read and agreed to the published version of the manuscript.  
This research work was supported by the Project \"Opportunities for olive oil value chain enhancement through the by-products valorization (OLIVEN)\", funded through the ARIMNet2 2017 Joint Call by the Agencia Estatal de Investigacion (Spain) under the reference number: PCI2018-093255. ARIMNet2 (ERANET) has received funding from the European Union within the Seventh Framework Program for research, technological development and demonstration activities under grant agreement no. 618127. Additionally, R.A. gratefully acknowledges financial support from Ministerio de Universidades under the FPU Program (ref. FPU19/00930).