Techno-Economic Analysis of Power Production by Using Waste Biomass Gasification

Energy recovery from waste biomass can have significant impacts on the most pressing development challenges of rural poverty and environmental damages. In this paper, a techno-economic analysis is carried out for electricity generation by using timber and wood waste (T & WW) gasification in Iceland. Different expenses were considered, like capital, installation, engineering, operation and maintenance costs and the interest rate of the investment. Regarding to revenues, they come from of the electricity sale and the fee paid by the Icelandic municipalities for waste collection and disposal. The economic feasibility was conducted based on the economic indicators of net present value (NPV) and discounted payback period (DPP), bringing togeth-er three different subgroups based on gasifier capacities, subgroup a: 50 kW, subgroup b: 100 kW and subgroup c: 200 kW. The results show that total cost increases as the implemented power is increased. This indicator varies from 1228.6 k€ for subgroups a to 1334.7 k€ for subgroups b and 1479.5 k€ for subgroups c. It is worth mentioning that NPV is positive for three subgroups and it grows as gasifier scale is extended. NPV is about 122 k€ (111,020 $), 1824 k€ (1,659,840 $) and 4392 k€ (3,996,720 $) for subgroups a, b and c, re-spectively. Moreover, DPP has an inversely proportional to the installed ca-pacity. It is around 5.5 years (subgroups a), 9.5 months (subgroups b) and 6 months (subgroups c). The obtained results confirm that using small scale waste biomass gasification integrated with power generation could be tech-no-economically feasible for remote area in Iceland.


Introduction
The rapid development of global economy, increasing population and living standards has been posing great pressure on energy resources and the environment. There is an urgency to use local renewable energies to promote local development and also reduce carbon emission. Waste biomass is an abundant and renewable energy that creates low net CO 2 emission. It is also the only suitable and primary energy resource that can provide transportation fuels [1] [2] [3]. Biomass gasification is an attractive option that is getting huge attention for conversion of different feedstocks to energy. In the gasification, a partial oxidation at elevated temperature (600˚C -1700˚C) is happened that converts organic components to a Synthesis Gas (syngas), consisting mainly of CO, H 2 , CH 4 , tars, inorganic impurities and particulates [4] [5].
Beneficially, waste biomass gasification can be applied for small/medium scales that lead to dramatic reduction of some pollutants emission as furans, dioxins, and NOx and the possibility of the utilization of the syngas in high efficiency thermal devices like internal combustion engine and gas turbines [6]. Hence, waste biomass gasification can be installed as a reliable energy supply technology for places which are far from the central energy networks and require district heat and power systems [7] [8] [9].
In this paper, we will explore the potential of timber and wood waste (T & WW) gasification for energy production in small communities in Iceland, (T & WW is the most existing biomass feedstock in this country). In this way, a techno-economic analysis of T & WW gasification facilities integrated with electricity generation unit will be directed for three subgroups with different gasifier installed power, 1): 50 kW, 2): 100 kW and 3): 200 kW to propose a sustainable waste to power system adapted with conditions in Iceland.  Table 1.

Process Description
T & WW is transferred from the waste fields to pre-processing part that is next to gasification and electricity generation unit. Diesel fuel is used in trucks  for transportation and electricity is applied for driving force and heat generation over the process. The electricity production in Iceland is derived from geothermal and hydropower that makes Iceland's main source of clean energy. The gasification process consists of drying, pyrolysis, combustion and gasification [11].
In this work the down draft reactors are considered that operate at atmospheric pressure, to gasify T & WW and air is used as the gasification agent, resulting in

Techno-Economic Assessment
In the economic assessment, all prices are expressed in K€ (kilo-euro) and the interest rate is 8%. A computer program has been developed to investigate eco- where n CF is the annual cash flow, being the difference between Revenues (R) Journal of Power and Energy Engineering and Expenditures (E), Operation and Maintenance Costs (C O&M ), r is the discount rate, C c is the total capital costs of investment and t is the lifetime of the investment (15 years). DPP is calculated according to Equation (2): The periodic cash flow, with all the revenues and expenditures, is calculated by considering the incomes from the generated electricity, and the credits for the Waste Treatment Bill (WTB) [6]. The expenditures also include the C c and C O&M . C c is divided into three categories: hardware price (C g ), installation cost (25% of C g ) and engineering costs, the engineering costs includes engineering and design (13% of C g ), purchasing & construction (14% of C g ), fuel handling/preparation (9% of C g ) and electrical/balance of plant (6% of C g ) [17] [18]. C g is the price of gasifier system overally on the basis of various capacities. In this work, we extracted gasifier prices from various companies [19] [20]. C g was considered 73.6 k€, 105.5 k€ and 147.5 k€ for 50 kW, 100 kW and 200 kW, respectively.
The whole yearly C O&M can be determined by the sum of the costs for the maintenance cost (2% of C c ), insurance and tax (2% of C c ), waste disposal (15% of C c ), electricity cost, liquid fuel cost and personnel cost. Electricity costs are  The total cost of the generation plant for each subgroup is shown in Figure 3.

Results
The total cost increases as the installed power grows, it is about 1228.6 k€ (Subgroup a), 1334.7 k€ (Subgroup b) and 1479.5 k€ (Subgroup c). In addition, Figure 4 depicts the percentage shares of hardware, installation, engineering and annual

Conclusion
In this work, techno-economic of power production plant that utilized syngas from a timber and wood waste gasification process in Iceland was investigated.
The technical assessment focused mainly on input waste, and installed power. The should be emphasized that NPV is positive for three subgroups and it grows as gasifier scale is extended. The NPV in subgroup c, is averagely 58% and 97% higher than subgroups b and a, respectively. NPV is about 122 k€, 1824 k€ and 4392 k€ for subgroups a, b and c, respectively. Moreover, DPP has an inversely proportional to the installed capacity. It is around 5.5 years (subgroups a), 9.5 months (subgroups b) and 6 months (subgroups c). Finally, the obtained results confirm that using small scale waste biomass gasification integrated with power generation could be techno-economically feasible for remote area in Iceland.