São Paulo-Based Study Shows Substituting Diesel for LNG can Boost Fuel Economy up to 60%

The replacement of diesel oil by liquefied natural gas (LNG) for cargo transportation in São Paulo, Brazil would possibly result in a substantial reduction in greenhouse gas (GHG) emissions and fuel costs as well as other pollutants. This was put forth by the Research Centre for Gas Innovation (RCGI) in a study, which is supported by the São Paulo Research Foundation – FAPESP – and Shell.

Located at the Engineering School of the University of São Paulo (Poli-USP), the RCGI is one of the Engineering Research Centers (ERCs) supported by FAPESP in collaboration with large companies.

“The biggest benefits, both in terms of pollution reductions and in prices of the fuels being discussed herein, are perceived in São Paulo and Campinas, which are regions with greater potential for substituting diesel oil with LNG and where diesel oil is more expensive than it is in the rest of the State. Our results show that in São Paulo, LNG can be up to 60% cheaper than diesel oil,” said Dominique Mouette, Professor in the School of Arts, Sciences, and Humanities at the University of São Paulo (EACH-USP), in an RCGI press communiqué. Mouette is chief author of the article and head of the RCGI project concentrating on the feasibility of a Blue Corridor in São Paulo State.

The study’s objective, which resulted in an article published in Science of Total Environment, was to assess the environmental and economic profits of replacing diesel oil with LNG for the purpose of creating a Blue Corridor in the state. This concept can be observed in Russia and defines routes on which trucks use LNG in the place of diesel oil.

LNG is acquired by cooling natural gas to -163 °C. Gas is condensed such that its volume is condensed up to 600 times, rendering it possible to be conveyed using cryogenic carts to locations situated far from oil ducts.

To examine the replacement of diesel with LNG, the study reflected on four scenarios. “Within the best scenario, the use of LNG would reduce fuel costs by up to 40%; equivalent CO₂ emissions [a measure used to compare the potential heating effect among several greenhouse gases (GHGs), also known as CO₂-eq] by 5.2%; particulate materials by 88%; nitrogen oxides (NOx) by 75%; and would eliminate hydrocarbon emissions,” states Pedro Gerber Machado, a scientist at the University of São Paulo’s Institute of Energy and Environment and co-author of the article.

“The methodology initially considered two contexts: one for the geographical regions served by gas pipelines, called the Restricted Scenario (RS), and another covering the 16 administrative regions of the state, called the State Scenario (SS). Both scenarios had different versions of the Blue Corridor, with 3,100 and 8,900 kilometers of roads, respectively,” Machado explained.

According to Machado, with each scenario, two forms of LNG distribution were looked into: the first one looked at a centralized liquefaction with road distribution and produced two sub-scenarios, a State Scenario with Centralized Liquefaction (SSCL) and a Restricted Scenario with Centralized Liquefaction (RSCL). The second would look into the liquefaction locally in the region where it would be used, which would remove the need for distributing LNG on highways. Based on this scenario, two more sub-scenarios were obtained: the State Scenario with Hybrid Local and Central Liquefaction (SSHL) and the Restricted Scenario with Local Liquefaction (RSLL).

Cost comparison

The RSLL scenario presents the lowest average price difference for the consumer between LNG and diesel, which means that, in this case, the delivery process of LNG is more expensive, as influenced by the scale factor and greater operating costs. The RSCL scenario offers the lowest gas price for the consumer, that is, 12 dollars per MMBTU (million British thermal units), whereas diesel, in this same scenario, would cost 22.01 dollars per MMBTU. The difference in price between LNG and diesel, in this scenario, is also the largest: 10.01 dollars per MMBTU.

Pedro Gerber Machado, Study Co-Author and Scientist, Institute of Energy and Environment, University of São Paulo

But, the RSLL scenario was planned for within the context of a shorter corridor, where the investment would be US$ 243.40 per meter. The SSHL scenario, in contrast, has the lowest investment per meter of the four scenarios (US$ 122.10 per meter).

Emissions avoided

Machado states that to measure the GHG and pollutant emissions, only the two macro-scenarios were considered: SS and RS. “When using LNG, the GHG emissions are different from diesel oil emissions due to CH₄ and N₂O, which are greenhouse gases with potential for global warming. If the fuel used is diesel, CO₂ is responsible for 99% of the emissions of CO₂-eq, and if the fuel used is LNG, it represents 82% of the CO₂-eq emissions, while CH₄ is responsible for 10% and N₂O for 8%,” he explains.

Concerning the GHG emissions produced by the logistics of shipping LNG, the worst-case scenario refers to the SSCL and agrees to 1% of the total CO₂-eq discharged with the use of trucks. In the SCHL, the logistics signify 0.34% of the emissions, and in the RSCL, the logistics match 0.28% of the emissions.

With regards to pollutants, in the RS scenario, 119,129 tons of emissions from particulate matter (PM) would be prevented: 7.3 million tons of NOx and 209,230 tons of hydrocarbon (HC). In the SS scenario, the advantages are even greater, with decreases of 163,000 tons of MP, 10 million tons of NOx, and 286,000 tons of HC.

When one compares the burning of diesel oil and natural gas, the decrease of 5.2% in GHG emissions, which was seen in the State Scenario, might not be so significant, but there are substantial reductions in local pollutants – NOx, PM, and HC saw reductions of 75%, 88%, and 100%, respectively.

However, irrespective of the economic and environmental benefits presented, LNG still faces regulatory hurdles to its common use in the transportation industry.

It is not regulated to be used as a fuel for vehicles in Brazil. Most of the LNG used here is compressed natural gas (CNG).

Dominique Mouette, Professor, School of Arts, Sciences, and Humanities, University of São Paulo

The research paper can be found in the journal Science of Total Environment, entitled “Costs and emissions assessment of a Blue Corridor in a Brazilian reality: The use of liquefied natural gas in transportation,” by Dominique Mouette Denis Fraga, Drielli Peyerl, Pedro Gerber Machado, Raquel Rocha Borges, Thiago Luis Felipe Brito, Lena Ayano Shimomaebara, and Edmilson Moutinho dos Santos.