Two birds, one stone: China’s potential for zero waste and nationwide ethanol

Guess what has become a hot topic in China nowadays? Wastes! Policymakers are dedicated to developing strategic plans for zero-waste cities, cities are putting money into new waste-treatment infrastructure, and residents are actively learning about and participating in waste sorting. All of these efforts combine to create a new waste stream with many potential uses. Meanwhile, a subject of heated debate is China’s plan to expand bioethanol production and implement E10—i.e., gasoline that contains 10% ethanol—nationwide this year.

While you might see these as two discrete topics, I’m connecting the dots. We previously showed that municipal solid waste (MSW), a type of cellulosic feedstock, can be used to produce second-generation biofuels, and the technology could bring significant climate benefits. So, here’s the idea: Why not convert MSW to cellulosic ethanol to achieve two policy goals at one stroke?

MSW is the everyday items people throw away like food, paper, and plastics—and China is a big producer. In 2018, 200 major cities in China generated more than 200 million tonnes of MSW, accounting for approximately 10% of the world’s total. More than half of the MSW in China ends up in landfill and about 45% is incinerated. This means that to achieve zero waste, China will have to find alternatives to landfill. While incineration offers the benefit of power generation, it is less ideal because it not only releases hazardous air pollutants including acid gases and particulate matter, which could lead to adverse health impacts, but also results in high greenhouse gas (GHG) emissions during combustion. Converting MSW to ethanol could be a more climate-sound solution for waste-to-energy and it fits nicely with ambitious ethanol goals.

In 2017, 15 ministries in China together released a bioethanol-expansion plan that includes a goal of nationwide ethanol blending for vehicles by 2020; the purpose is to shift from fossil fuels to low-carbon renewable fuels, and China’s most recent annual on-road gasoline consumption was about 172 billion liters. A 10% ethanol blending nationwide would thus require more than 17 billion liters of ethanol, significantly higher than China’s current production of less than 3 billion liters per year. If all of the organic material in China’s MSW, which is approximately 65%, was used to make ethanol, China could add another 14 billion liters to its current production and almost reach the 10% blending volume. But so far, it’s likely that virtually none of the ethanol produced in China comes from MSW.

At present, the main feedstocks for ethanol production in China by far are corn kernel and cassava. Because they are crops, their availability is greatly affected by multiple factors, including environmental conditions, food demand, and the circumstances of international trade. Therefore, the remaining volume of corn and cassava available for ethanol production is somewhat uncertain. Earlier this year, a news article suspected that the E10 plan might have to be suspended due to a significant fall in corn stocks, but no official announcement has been made. The amount of MSW is unlikely to fluctuate as much as crop feedstocks, either intra-annually or inter-annually. Instead, as China’s MSW generation is increasing, its use as feedstock could introduce a level of stability into the ethanol industry. And because the sorting, collection, and distribution system is evolving thanks to the series of waste policies, ethanol producers could take advantage of this feedstock supply chain of MSW.

Moreover, we previously found that the direct emissions of MSW ethanol could provide 37% GHG savings from gasoline. If we further account for the avoided methane emissions from MSW in landfill using China-specific data, the GHG savings could reach more than 100%. As a comparison, the U.S. Environmental Protection Agency estimates that corn ethanol provides 21% GHG savings. Given that GHG reduction was one of the key drivers behind China’s expansion of ethanol, MSW ethanol is especially well suited.

As fantastic as this idea might sound, it won’t be easy to realize, and that’s mostly because of the limited refinery capacity. Right now, the built capacity of cellulosic ethanol in China is up to about 65 million liters. We’re not sure how much of it is MSW-based, but it is highly likely to be a very small portion. Even for crop-based ethanol, a conventional technique, the capacity merely exceeds 5 billion liters. To meet the nationwide ethanol blending goal this year, China would need to ramp up the capacity fast and significantly. Given that the capital cost of building a cellulosic ethanol plant is typically high, supportive mechanisms are needed. In one of our previous studies, we highlighted how direct financial support from the government, such as grant funding, is an effective measure for the early development of advanced biofuels, including MSW ethanol. That’s because it helps mitigate the investment risks and attracts both project developers and investors.

Also, there remain concerns that ethanol blending might lead to elevated evaporative emissions, or the escape of gasoline vapor from the vehicle’s fuel tank. As China is making progress on nationwide implementation of the China 6 emission standard for light-duty vehicles, any expansion of nationwide ethanol blending needs to go hand-in-hand with the emission standard, to ensure that adverse environmental impacts aren’t introduced. Implementing a robust evaporative emission control system on vehicles can effectively prevent such emissions.

Despite the hurdles, MSW ethanol is still worth trying. Scaling up MSW ethanol production in China is quite compatible with the series of actions that support zero-waste cities and meeting the national ethanol blending target. Certainly, a lot more refinery capacity is needed to make this one stone hit these two giant birds. But how wonderful would it be if solving one environmental issue was, in itself, the way to achieve another environmental objective?

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