Rubber Chronicle 19: CO2e Emissions of Natural Rubber, Neoprene, Geoprene and SBR
Yulex’ claims that our natural rubber-based foams emit 80% less CO2 emissions compared to petroleum-based neoprene, geoprene and styrene butadiene rubber (SBR). Here, we discuss additional independent published scientific data and self-reported data to regulatory agencies supporting this claim.
There are several ways to analyze and compare the energy consumption of materials generally:
We are a branded products company that develops our own certified natural rubber supply chains including our own grade of natural rubber and latex products as well as natural rubber-based components such as Yulex foams. To date, we do not make finished goods.
Because we are not a finished goods manufacturer, we are not able to compare energy consumption using methods 1 (LCA) and 3 (Production Process Analysis) reserved for finished goods. Hence, we do not have access to the many unique supply chain logistics for finished goods including procurement, production and scheduling, inventory management, transportation, warehousing, fulfillment, and information systems.
Also, because the production of Yulex foam and neoprene foam are virtually identical– meaning except for the raw material that makes up the polymer ingredient, they both use the same equipment, the same non-polymer ingredients (e.g., vulcanizing and blowing agents, fillers), and have the same energy inputs for the foam production. So, we will not compare foam production as we assume they are substantially similar.
We focus on methods 2 (Energy Intensity) directed to the raw materials that go into production of Yulex foam and benchmarking (method 4) that against the raw material that goes into production of neoprene foam, geoprene foam- natural rubber, polychloroprene, and acetylene respectively.
CO2 equivalent or “CO2e” is used to compare the global warming potential of different greenhouse gases (“GHG”) on their ability to trap heat in the atmosphere. It allows for the comparison of emissions across different GHG by expressing their respective impact in terms of equivalent amount of carbon dioxide (CO2e) that would cause the same level of global warming. CO2 is the most common GHG and therefore used as the reference gas. And by converting emissions of different GHG into CO2e, scientists can compare the total impact of all greenhouse gas emissions on the climate.
We use independent scientific sources and required self-reporting emissions data because they provide:
We encourage you to do your own analysis, check our numbers and participate in reasonable and fact-based debates.
Our new Equitable Ag (profit-sharing) certified natural rubber supply chain is from Vietnam and Thailand and produced by smallholders exclusively. Hence, in determining CO2e, we focused on a scientific journal publications that report energy consumption of small plantations held by smallholders. We scoured different databases and focused on a peer review scientific journal article by Warit Jawjit, et.al. (2010), “Greenhouse gas emissions from rubber industry in Thailand, ”Journal of Cleaner Production, Vol. 18, pp. 403–411 (“Jawjit”), which measures and reports data from smallholder plantations. Methods and management of plantations and production of block rubber have remained unchanged for over a century, so this 2010 paper is still relevant- even if methodologies of GHG capture may have changed, this does not necessarily change the GHG reported in Jawjit.
Jawjit quantified emissions from rubber mills that process fresh tree latex from 2 types of smallholder plantations: 1) less than 20 years old on deforested forest land, and 2) those older than 60 years old on cultivated land. Smallholders on Type 1or type 2 plantations collect tree latex the same way. The overall GHG emissions (or CO2e) is the sum of emissions from rubber plantations and rubber mills.
Jawjit calculate emissions of the greenhouse gases CO2, CH4 and N2O. The emissions associated with rubber products are first calculated in term of kg CO2 (CH4, N2O) per ton of rubber product (fresh latex, concentrated latex, STR 20, RSS), and then converted to CO2-equivalents (or CO2e) using Global Warming Potentials (GWP). The GWPs are 21 and 310 for CH4 and N2O, respectively (IPCC, 2006).
Yulex natural rubber supply chains in Vietnam and Thailand consists of about 1000 smallholders. Their production practices are substantially similar to that described by Jawjit. Their homes are on the same land plot as their plantations, most do not own cars but motorbikes, latex collection centers are located near their homes/plantations and transport of latex is by motorbike, animal manure for fertilizer is preferred (mostly because it is also cheaper), little to no pesticide is used, most smallholders tap their own tree, and if not employ someone in the same village. The majority of GHG emissions for production of block rubber is from the rubber mill and not from the smallholder plantations, which is consistent with Jawjit.
First, GHG emissions from plantations exceed emissions from rubber mills for production of latex and ribbed smoked sheets, 30% and 5%,respectively. In contrast, GHG emissions from rubber mills for block rubber production is significantly more than emissions from the plantations, 44% more.
Second, Jawjit showed that production and use of synthetic Nitrogen fertilizers is the most important source of GHGs for all three rubber products and accounts for about 30–50% of total GHG emissions. Synthetic fertilizers are sources of GHG emissions because their production results in high GHG emissions and by-products such as N2O, which contribute to GHG emissions.
Jawjit suggest that a shift from synthetic Nitrogen fertilizers to animal manure, or to renewable fertilizers, would reduce GHG emissions per ton of rubber product produced by at least one-third. Most of our smallholders live in rural areas and prefer animal manure fertilizer- even before PEFC and/or FSC certification.
For polychloroprene production, crude oil is refined to make naphtha and further refined to make butadiene. Butadiene is the primary chemical used in production of polychloroprene or neoprene. See the Petrochemical Manufacturing Basics graphic below.
In the USA, the Environmental Protection Agency (“EPA”) requires by law that large sources of GHG emissions, such as that from the petrochemical plants, report their annual GHG emissions to the EPA under its Greenhouse Gas Reporting Program (“GHGRP”). Hence, GHG emissions from petrochemical plants that make synthetic rubber are well documented in the USA. The EPA GHGRP emissions data for 2021 for the Denka Performance Elastomer (DPE) petrochemical plant (La Place, Louisiana), the only plant making polychloroprene in the USA, reported 95,255.8 metric ton of CO2e. DPE makes polychloroprene from butadiene at that facility. To determine the metric ton of CO2e per metric ton of product (or polychloroprene), we divided this number by the total capacity of 50,000 metric tons published by DPE: 95,255.8 / 50,000 = 1.90 metric ton CO2 per metric ton of polychloroprene.
In a recent study by Flannery & Mares, Greenhouse Gas Index (“GGI) values were used to track the GHG emissions of products derived from fossil resources along the production and supply chain. The report is focused on North American Industry Classification System (NAICS) 325212 of 30 products. They report CO2e values for Butadiene and Styrene Butadiene Rubber (or “SBR”) as in Table 2 below. The GGI values were derived from the US companies that report the amount of CO2emissions from the production of their synthetic rubber products to regulators.
See, Brian P. Flannery and Jan W. Mares (2022), “Greenhouse Gas Index for Products in 39 Industrial Sectors: Synthetic Rubber NAICS CODE 325212,” Resources for the Future, September 2022, pp. 1-16 (“Flannery & Mares”).
*To obtain the total CO2e for production of polychloroprene from butadiene, we added the CO2e from the production of butadiene (4.59), and the CO2e from the production of polychloroprene from butadiene (1.90), for a total of 6.49, which is higher than production of Butadiene alone.
Polychloroprene can be made from butadiene as described above, but it can also be made from acetylene, which is made from calcium carbide, which is made from limestone extraction or mining (or blasting). Limestone-based neoprene production is not made in the USA, so we turned to China, which is the largest producer and consumer of calcium carbide worldwide. See, Suisui Zhang, Jingying Li, Gang Li, Yan Nie, Luyao Qiang, Boyang Bai, Xiaoxun Ma(2021), “Life cycle assessment of acetylene production from calcium carbide and methane in China,” Journal of Cleaner Production 322 (2021), Vol. 322, pp. 1-9 ("Zhang").
Zhang describe 3 methods for production of acetylene from limestone commonly used in China: calcium carbide, methane partial oxidation and the plasma method (currently being industrialized).
Figures 1 and 2 from Zhang describe the calcium carbide and the methane partial oxidation methods; and Table 3 describes CO2e emissions from the 3 methods described in Zhang. The most common method is the calcium carbide method- emitting 14.5 metric tons of CO2e per metric ton of acetylene.
Jawjit reported that 0.70 metric ton of CO2e per metric ton of block rubber, the raw material for Yulex foam. Compare this to the 6.49 metric ton of CO2e per metric ton of neoprene and the percentage of reduction is: (6.49 - 0.70) / 6.49 = 89%.
Stated simply, the raw material that goes into making neoprene produces 89% more CO2e than the raw material that goes into making Yulex foam. This is consistent with that supported by Flannery & Mares, who stated that “the major contributors to the GGI of these products are the GGIs of their raw materials (e.g., butadiene, ethylene, propylene, styrene, and others that we cover in the module on petrochemicals).”
Production of natural block rubber is also significantly less than SBR, and the percentage of reduction is: (5.55 - 0.70) / 5.55 = 87%.
Zhang reported metric ton of CO2e per metric ton of acetylene for the 3 methods used to produce acetylene. See Table 3 above or Table 7 in Zhang. The 2 common methods of acetylene production alone are 86% and 95% higher CO2e levels than natural rubber.
Calcium Carbide method: (14.5 - 0.70) / 14.5 = 95%; Methane Partial Oxidation method: (5.02 - 0.70) / 5.02 = 86%.
So, although we do not have CO2e emissions for geoprene production from acetylene, the CO2e emissions for acetylene alone is significantly greater than natural rubber. Therefore, it is entirely expected and reasonable that the additional CO2e to make geoprene from acetylene would be even greater than 86 - 95% CO2e than natural rubber production.
PEFC and FSC promote and in many instances require:
Yulex is not new to Deforestation-free supply chains. It has been at our core from the beginning. For over a decade, we have been developing, partnering, and sourcing only certified natural rubber. We introduced FSC-certified natural rubber to the consumer industry with Patagonia. Since working in Southeast Asia, and working with smallholders, we now also partner with PEFC.
Our GHG emissions analysis back in 2014-2015 was based on our then existing data with our rubber processing plant in Arizona and our own source of Guayule natural rubber and/or certified-natural rubber from our partners in Guatemala. Our certified natural rubber supply chains in Southeast Asia are different because we work with smallholders exclusively and not large plantation estates. Thus, we decided to take another look at GHG emissions.
The result is that when compared to chloroprene (neoprene), geoprene and SBR, these synthetic rubbers emit greater than 80% CO2e compared to natural rubber. See the Summary Table 4 below. Our analysis is not perfect. There are gaps, and we hope to work with partner brands to do a full study.
Note: Not all references researched are cited, only those cited in the analysis.
Brian P. Flannery and Jan W. Mares (2022), “Greenhouse Gas Index for Products in 39Industrial Sectors: Synthetic Rubber NAICS CODE 325212,” Resources for the Future, September 2022, pp. 1-16
Jawjit, Warit (2010), Greenhouse gas emissions from rubber industry in Thailand, Journal of cleaner production Volume: 18 Issue 5, pp. 403-411.
Suisui Zhang, Jingying Li, Gang Li, Yan Nie, Luyao Qiang, Boyang Bai, Xiaoxun Ma(2021), “Life cycle assessment of acetylene production from calcium carbide and methane in China,” Journal of Cleaner Production 322 (2021), Vol. 322, pp. 1-9.
https://www.epa.gov/ghgreporting/subpart-w-petroleum-and-natural-gas-systems
https://www.epa.gov/ghgreporting/ghgrp-reported-data
https://www.afpm.org/newsroom/infographic/petrochemical-manufacturing-basics
