CS7: Energy Transition

Remote communities in the Brazilian Amazon still rely on diesel-fired isolated grids, which leads to high generation costs, greenhouse-gas emissions, and fuel-supply risks. This paper asks: which hybrid configurations minimize system cost and emissions while fully meeting hourly demand in an Amazonian isolated system? We study the municipality of Tefé-AM using urbs, an open-source linear optimization model that jointly determines hourly dispatch and cost-optimal capacity expansion. Inputs include an hourly load profile (regional proxy normalized to the local average demand), an annual solar PV generation time series for Tefé (weather-based simulation), and techno-economic parameters (CAPEX/OPEX, lifetime, WACC) for PV, battery storage, and thermal plants. Fuel prices for diesel and natural gas are included, together with a carbon price to internalize emissions costs. The formulation enforces hourly energy balance, storage operating limits (efficiency and state of charge), and explicitly tracks renewable curtailment; robustness is assessed through sensitivity analysis (carbon price in this submission, and in the full design: PV/BESS costs, WACC, and fuel prices). Results show that the current diesel-only configuration reaches LCOE ≈ 403 USD/MWh and emits ~120 ktonCO₂/year. Adding PV reduces LCOE to ~300 USD/MWh and emissions to ~80 ktonCO₂/year. With PV + batteries, LCOE drops to ~226 USD/MWh and emissions to ~5 ktonCO₂/year, with moderate curtailment. The PV + batteries + natural gas option delivers the lowest LCOE (~224 USD/MWh) with ~6 ktonCO₂/year, as gas provides a lower-carbon backup that reduces renewable overbuild needs. A fully renewable PV + battery case eliminates local emissions but exhibits high curtailment (~112 GWh/year) and a higher LCOE (~291 USD/MWh). These findings provide actionable insights for auction design and public programs aimed at reducing subsidy burdens and accelerating decarbonization in Amazonian isolated grids.

This paper assesses the potential contribution of bioenergy with carbon capture and storage (BECCS) to industrial decarbonization in Brazil, with a focus on the sugarcane sector and the option of geological CO₂ storage in basalt formations. The central research question is whether BECCS, when integrated into existing sugar and ethanol mills, can represent an economically feasible mitigation pathway under the Brazilian context.
The analysis draws on a structured review of the techno-economic literature on BECCS applied to sugar and ethanol mills (ENSINAS, 2017), complemented by a spatial assessment of sugarcane production in Brazil (ANP, 2025) and the occurrence of major basalt formations (IBGE, 2005). Rather than optimizing a specific project design, the paper discusses the main stages of BECCS development and highlights the trade-offs that are most relevant from an economic perspective.
The reviewed studies indicate that CO₂ capture from alcoholic fermentation is generally more favorable than capture from biomass combustion, due to higher gas purity and lower associated energy penalties, although it may limit economies of scale (Restrepo-Valencia, 2019). With respect to geological storage, basalt formations offer enhanced long-term containment due to mineralization processes. Injection strategies, however, differ significantly in terms of cost and energy requirements. Options that emphasize storage security, such as CO₂ dissolved in water (Matter et al., 2016), are associated with substantially higher energy costs when compared to supercritical or cold liquid injection (Norton, 2024).
Overall, the results suggest that BECCS combined with basalt storage presents relevant mitigation potential in the Brazilian sugarcane sector, particularly due to the high concentration of mills located near basalt formations. However, its economic viability remains highly context dependent. The analysis identifies data gaps and highlights the need for further research incorporating updated cost parameters and local operating conditions to support more robust techno-economic assessments.

1. Introduction
Due to globalization, the volume of commodities traded by vessels has been increasing. In addition, greenhouse gas emissions from international shipping have increased significantly, accounting for approximately 2% of global emissions in 2022.
Parties have negotiated at the United Nations Framework Convention on Climate Change (UNFCCC) to address this issue. In 1996, the UNFCCC proposed eight options to allocate carbon dioxide emissions from international shipping to each country and region (Table.1). 

2. Methodology 
Analytic Hierarchy Process (AHP): Comparing and evaluating the eight options proposed by the UNFCCC by four criteria, i.e., feasibility, administrative burden, fairness, and evasion for this study. Then, a hierarchy chart was created to select one option from the eight proposed options.

3. Preliminary result
 We conducted a pairwise comparison of four criteria and obtained their weights shown in "Figure.2". Feasibility has the greatest weight, at 53.4%, followed by administrative burden (22.6%), fairness (12%), and evasion (12%). 



We calculated each criterion's evaluated values based on "Figure. 2" and questionnaires comparing one option with other options. Then, we compared each option by each criterion's evaluated values and obtained "Figure.3". 
 Option 1 received the highest scores in three of the four criteria. On the other hand, Option 7 received the lowest scores for both criteria, and the scores for the other two criteria were not particularly high. 



 Finally, an overall evaluation value was obtained and shown in "Figure.4" based on "Figure.3". Option 1 received the highest value, followed by Option 3, Option 8, and others.

4. Implications
As a result of this study, two criteria, feasibility and administrative burden, were critical factors in evaluating each alternative. Ultimately, since Option 1 yielded the highest value, we preliminarily recommend selecting it as the best alternative.

Reducing greenhouse gas emissions requires rapid power-sector decarbonization, yet increasing the share of variable renewable energy (VRE) intensifies the operational challenge of matching supply and demand. Uruguay is an informative benchmark for deep decarbonization: it already operates with a predominantly renewable electricity matrix and is planning further wind and solar expansion. We assess reliability risk through the hourly energy balance, defined as the demand-normalized gap between VRE generation (solar-wind) and demand. Negative realizations correspond to deficit episodes in which the system must rely on hydro releases, thermal dispatch, or imports, increasing exposure to price volatility and operational costs.
We use a financial risk framework to quantify downside and tail exposure with expected shortfall (CVaR). We then evaluate Uruguay's system under the operator's 2043 expansion plan and compare it with alternative expansion pathways. These pathways adjust the spatial and technological composition of renewables to leverage complementarity across wind and solar resources. Our findings indicate that the insertion of additional renewables can mitigate downside and tail risk in the energy balance, which are events characterized by low VRE output coinciding with high demand. The most significant improvements are achieved when the expansion plan explicitly considers spatial and technological complementarity. In contrast, variance-based smoothing strategies primarily reduce overall dispersion (standard deviation) around typical outcomes but do not directly target rare, high-impact deficit states. This study contributes to the literature by providing a planning framework based on downside risk that links renewable portfolio composition to reliability outcomes in high-VRE systems. It also shows how deep decarbonization can be accompanied by improved security of supply when expansion planning is guided by downside-risk considerations.