As part of the City of Tucson’s bold 2030 carbon neutrality plan, GHD delivered a feasibility study for interim utilization of the Los Reales Landfill gas (LFG) to power the city’s maintenance vehicle fleet and transit buses operated by Sun Tran. The project’s mission was to investigate the transition to a full RNG fleet as an interim solution and a zero emissions fleet through electrification to meet long-term sustainability and climate action goals. The feasibility study is phase one of a multi-phase journey to a fully decarbonized transportation solution and GHD is happy to be part of the city’s solution to meet their 2030 goals.

Utilizing GHD’s Zero Emissions Vehicle Optimization (ZEVO) tool, we provided a fleet assessment for LNG utilization and subsequent electrification. We started by separating the city’s vehicles into two fleet groups for analysis: non-revenue vehicles, including refuse trucks and maintenance vehicles; and revenue-generating vehicles, such as conventional transit buses. Using ZEVO’s statistical model, each asset was assigned a score to determine its operational viability into different future scenarios. The statistical model predicted the viability of each asset by using specific metrics such as fuel type, odometer reading, fuel efficiency, maintenance costs per unit. The summarized data was incorporated into ZEVO’s economic decision-making model, where we created various scenarios for fleet transition. Each scenario was run through financial models to create different CAPEX and OPEX options. Utility Modelling was also performed to show the daily peak demand (KW) for electricity. Lastly, environmental models were run to confirm each scenario’s overall GHG emissions and other output pollutants. After an evaluation stage, the preferred scenario was converted into a 3-Phase fleet transition plan where, through attrition, the entire fleet would be converted to CNG units. As the older CNG units come up to retirement, they will be replaced with the specified ZEVs. This pathway presented significant carbon emission savings and did not require immediate and untenable capital investment.

We developed a high-level implementation strategy for the city’s entire fleet and a procurement model to achieve that strategy. By utilizing the extensive modules of ZEVO, we opened a window into the city’s decarbonization ambitions and provided confidence in their path forward, while removing the risk of the unknown. GHD continues to assist the city in transitioning their fleets to zero emissions by 2030.