Abstract
This contribution presents an hourly-based optimization of a biogas supply network to generate electricity, heat and organic fertilizer while considering multiple objectives and auction trading prices of electricity. The optimization model is formulated as a mixed-integer linear programming (MILP) utilizing a four-layer biogas supply chain. The model accounts for biogas plants based on two capacity levels of methane to produce on average 1 ± 0.1 MW and 5 ± 0.2 MW electricity. Three objectives are put forward: i) maximization of economic profit, ii) maximization of economic profit while considering cost/benefits from greenhouse gas (GHG) emissions (economic+GHG profit) and iii) maximization of sustainability profit. The results show that the economic profit accrued on hourly-based auction trading prices is negative (loss), hence, four additional scenarios are put forward: i) a scenario whereby carbon prices are steadily increased to the prevalent eco-costs/eco-benefits of global warming; ii) a scenario whereby all the electricity auction trading prices are multiplied by certain factors to find the profitability breakeven factor, iii) a scenario whereby shorter time periods are applied, and investment cost of biogas storage is reduced showing a relationship between cost, volume of biogas stored and the variations in electricity production and (iv) a scenario whereby the capacity of the biogas plant is varied from 1 MW and 5 MW as it affects economics of the process. The models are applied to an illustrative case study of agricultural biogas plants in Slovenia where a maximum of three biogas plants could be selected. The results hence present the effects of the simultaneous relationship of economic profit, economic+GHG profit and sustainability profit on the supply and its benefit to decision-making.
Highlights
In December 2015, over 190 countries across the globe acceded to employing activities and technologies that minimize the effects of global climate change [1]
This study presents a model showcasing the effects of economic profit, sustainability profit and economic+greenhouse gas (GHG) profit on the supply chain network production of electricity based on two capacities (1 MW and 5 MW) over hourly, daily, and monthly timeframes
A sensitivity analysis involving the variation of the auction trading prices of electricity against maximizing the economic profit shows that the breakeven value for economic profit may only be obtained beyond the doubling of the auction trading prices
Summary
In December 2015, over 190 countries across the globe acceded to employing activities and technologies that minimize the effects of global climate change [1]. Among the technologies considered is to increase the utilization of biomass-derived energy sources ( called bioenergy). It is noteworthy that this policy only considers the use of non-edible feedstock retrieved from lands unsuitable for agriculture to prevent food versus fuel conflicts. In another case, the (2020) 2:3 government of Ghana enacted a biofuels policy to substitute petroleum fuels with 10% biofuels by 2020 and a further increase to 20% biofuels incorporation by 2030 [6]. Its current policy (13th five-year spanning 2016–2020) indicates that on or before the year 2020, the rate of utilization of energy derived from biomass should exceed 58∙106 t/y of standard coal while biogas employed for cooking should reach 80∙106 m3 and electricity generated from the same biogas should be at least 500 MWe [8]
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