## 4 Techno-Economic Assessment  
This last section aims at demonstrating the techno-economic feasibility of the proposed biomass gasification CHP plant for an off-grid olive oil mill in the region of Marrakech-Safi, Morocco. The gasification plant consists of a biomass storage silo, a downdraft gasifier, a producer gas conditioning unit and engine-generator set fueled with the producer gas from biomass gasification. The techno-economic feasibility involves the comparison of two scenarios:  
* Current scenario. A 100 kVA (80 kW\({}_{\rm e}\)) engine-generator set fueled with 210 L/day of diesel is used to power the off-grid olive oil mill. The engine-generator set is rented at a monthly cost of EUR 2500. A cost of EUR 1.5/L is assumed for the diesel fuel. * Alternative scenario. A 100 kVA (80 kW\({}_{\rm e}\)) engine-generator set fueled with producer gas is used to power the off-grid olive oil mill. A gasification CHP plant fed with either olive cake pellets or pruning chips is used to generate the producer gas. The cost of the biomass feedstock used as fuel is negligible, as it is produced onsite. Listed below are all the considerations and assumptions made for the economic feasibility assessment of the alternative scenario:  
* The gasification plant operates continuously for 2 months (December and January) and only requires two monthly maintenance stops. The operational lifespan of the gasification plant for the economic feasibility assessment is estimated at 20 years [22]. * The cost of the gasification technology for CHP on a distributed scale is estimated at approximately EUR 3000/kW\({}_{\rm e}\) on a commercial scale. This value takes into account the cost of the gasifier, the producer gas conditioning unit and the engine-generator set, which for a 80 kW\({}_{\rm e}\) CHP plant would amount to EUR 240,000. For comparison, [PERSON] et al. [42] estimated a slightly higher power capital expenditure of EUR 3486/kW\({}_{\rm e}\) for a pilot-scale gasification plant (model PP20, All Power Labs, Berkeley, CA, USA) processing 12.6 ton/h of municipal solid waste in Portugal. The power capital expenditure considered in this work is also slightly below the value of EUR 3544/kW\({}_{\rm e}\) declared by [PERSON] et al. [43] for a gasification CHP plant fueled with municipal solid waste in the UK, although the reaction configuration was different (fluidized bed), as well as the power generation unit (combined cycle gas turbine). By contrast, a considerably lower investment cost of USD 2580/kW\({}_{\rm e}\) was reported  
Figure 11: Energy flow diagram of the gasification CHP plant fueled with olive cake pellets with a 10% moisture content (wet basis). by [PERSON] et al. [25] for an off-grid gasification CHP plant fueled with rice husk and plastic in Nigeria. In the work of [PERSON] et al. [44], a lower capital cost of EUR 1760/kW was assumed for the case of a 100 kW\({}_{\text{e}}\) gasification CHP plant fueled with forest biomass, while an even lower capital cost of EUR 1320/kW was assumed for the case of a 1000 kW plant as a result of economies of scale in the deployment of a larger unit. Thus, a capital expenditure of EUR 3000/kW\({}_{\text{e}}\) seems to be a conservative, and yet reasonable, assumption for the biomass gasification CHP plant considered in this work. * The civil works amount to EUR 15,000, while the biomass pretreatment cost (pelletizer or chipper) is estimated at around EUR 20,000. The fixed and installation costs of the gasification plant (civil works, electrical and mechanical assemblies) are estimated as 10% of the total investment. As a result, the turnkey cost of the gasification CHP plant amounts to roughly EUR 302,500. * The gasification plant was installed for self-consumption of renewable electricity during the whole olive oil production period, leading to a substantial reduction in the energy cost for the olive oil mill. An average electricity price of EUR 0.15/kWh was considered.