Analysis: Negative emissions tested at world’s first major BECCS facility

Decatur, Illinois, is a city built on corn. At the centre of its economy are two giant agribusinesses, Tate & Lyle and Archer Daniels Midland (ADM), which together grind thousands of bushels a day into syrups, sweeteners, ethanol fuel and other useful products.

Thanks to the second of these companies, Decatur is also a city that is built on CO₂— literally. For the past nine years, ADM has been part of an ongoing experiment to capture the emissions from its ethanol plant and trap it in the layer of sandstone that lies beneath the Illinois corn belt.

This is is calledcarbon capture and storage, a struggling technology that would see CO₂emissions collected and sequestered, rather than being released into the atmosphere and contributing to climate change.

Most carbon capture projects (andthere aren’t many) are attached to power plants or industrial units, capturing the CO₂released by burning fossil fuels or making products. In an ideal world, at least, this would make these processes carbon neutral.

But the project in Decatur goes further than this. The fact that it captures emissions released by fermenting corn, which absorbs CO₂when it grows, means that, overall, the process also captures CO₂from the atmosphere.

This process is known as bioenergy with carbon capture and storage — more commonly known by its acronym,BECCS．

The difficulty of actually reducing emissions quickly enough to meet global temperature targets means that BECCS is increasingly becoming a part of the climate change discussion. It is expected to feature as part of a UN science report due in 2018 on the challenges of limiting temperature rise to 1.5C.

At a UN meeting last week, French diplomat Laurence Tubianasummarisedsome of the challenges in response to a question about BECCS posed by Carbon Brief:

Importance of BECCS

With the UN’s new deal on climate change, the world has signed up to keeping global temperature rise to “well below” 2C, and to 1.5C if possible. Arecent studyhas shown that this half a degree makes a world of difference when it comes to the impacts, such as coral bleaching, sea level rise and heatwaves.

The trouble is that meeting this 2C goal is already looking like a challenge. Even with the recent round ofclimate pledgesdrawn up as part of the UN deal, countries are set to emit enough CO₂to push the planetwell beyondthis target, possibly to3.7C higherthan pre-industrial levels.

This is a cloud over the most vulnerable nations, such assmall island states, who are counting on the 1.5C target to ensure their survival.

But there is a glimmer of a silver lining. Even if countries overshoot the 2C target, there is some hope that the planet can subsequently get back down to this level, if humans are able to remove carbon dioxide emissions from the atmosphere.

This is a process known as “negative emissions”, or “carbon dioxide removal”. As Carbon Brief explained in detail earlier this year, there arevarious waysof going about it, ranging from the bizarre to the plausible.

None of them are without drawbacks, but BECCS is considered one of the more feasible methods of achieving this on a large scale.

The Intergovernmental Panel on Climate Change (IPCC) says that most scenarios that return a likely chance of staying below 2C rely on the“widespread deployment”of BECCS in the second half of the century —removalsof around 616 gigatonnes of CO₂(GtCO₂) by 2100.

Despite this, the technology remains untested and uncertain, and climate campaigners are increasingly raising risks such as land grabs and food security, aswitnessedat the latest round of UN climate negotiations.

So far, there are currently around 15 pilotprojectsaround the world. But 2016 could be a milestone. Before the year is out, ADM is hoping that its corn processing plant in Decatur could be the first to start using the technology on a large scale.

At the ethanol plant

As part of US efforts to reduce its CO₂emissions, the Department of Energy (DoE) isfundingthree CCS projects that will reduce emissions from industrial sources.

ADM’s ethanol plant was selected from 12 initial proposals to enter the design, construction and operation phase, receiving $141m in funding. Private sources have contributed the remainder of the total $208m.

One reason why this particular plant is viewed as a good bet for the DoE’s money is that ADM had already succeeded in sequestering amillion tonnesof CO₂over three years during a one-off pilot project (all tonnes are metric).

Between 2011 and 2014, CO₂was injected at a rate of 1,000 tonnes per day into the Mount Simon sandstone. But a million tonnes of captured CO₂is a trifle in the grand scheme ofglobal emissions．A typicalmedium-sized500 megawatt coal-fired power plant emits around three million tonnes every year.

The Mount Simon sandstone has proved ideal for CO₂storage during this experiment. It is very porous, meaning that CO₂can be stored in tiny holes in the rock, while lying beneath three layers of dense shale, which effectively cap the reservoir and prevent it from leaking.

The next part of the project is to scale it up to a commercial level. Together with the existing facilities, ADM’s ethanol plant aims to capture and store 2.26m tonnes of CO₂(MtCO₂) over a period of 2.5 years, at a rate of around 0.9MtCO₂a year. After years of delay, this process is expected to begin some time before the end of 2016.

When this happens, the CO₂将收集到的ADM corn-to-ethanol闭ntors in a pipeline, and variously compressed and dehydrated to an intense pressure before being injected into the sandstone. The fact that fermentation produces an extremely pure stream of CO₂means that its capture is easy relative to capturing the CO₂at a coal plant, for example.

In 2014, the IPCCcalledthis “the most relevant BECCS project” to date.Sallie Greenberg, the principal investigator on the project for the Midwest Geological Sequestration Consortium, tells Carbon Brief:

‘Negative emissions’

The project has obvious benefits. The 2.27Mt captured over the lifespan of the project are emissions that would have otherwise have been vented into the atmosphere, contributing to global temperature rise.

But does the installation of this $207m equipment mean that ADM’s ethanol plant will turn from a source of pollution to a sink, capable of reducing the overall volume of CO₂in the atmosphere?

To answer the question of whether the BECCS project generates “negative emissions” requires data concerning how much CO₂the corn absorbs as it grows, and whether this is exceeded by the emissions of the individual plant and the BECCS facility as it converts the corn to ethanol, and captures and buries the CO₂．

ADM reports the Decatur facility emissions to the EPA, but does not break this down to the level of individual plants, and did not respond to requests for comment for this article. This means it is difficult to assess whether the corn plant itself is rendered “carbon negative” by the project.

However, the Decatur facility, which is largely powered with natural gas, cannot be considered net carbon negative as a whole. The facility not only processes corn, but also a number of other products,includingvitamin E, soybean and glycols. These other plants are not fitted with CCS technology.

According to figuresreportedto the US Environmental Protection Agency by ADM, the Decatur facility as a whole emitted more than 5MtCO₂equivalent (CO₂e) in 2014.

Taking this as a rough proxy for its emissions in the near future (noting that ADM does not have an absolute emissions reduction target, only anintensity reduction target), the facility will emit 12.7MtCO₂in the 2.5 years that emissions are sequestered at the plant.

During the injection period, 2.27MtCO₂will be captured and buried. The process of capturing this CO₂will itself emit an additional 173,000tCO₂, according to the EPA’sEnvironmental Assessmentof the project. The fermentation element is only part of the process — additional CO₂will be released when the ethanol itself is burnt.

This takes the net total of sequestered CO₂to 2.1Mt, reducing the overall CO₂emissions of the plant by around 14%. This means that the plant as a whole will continue to emit around 10.5MtCO₂e over the three years of the project, or around 3.5MtCO₂e per year. This is almost four times as much as the amount sequestered.

It is also worth noting that the motivations for the project are not entirely environmental. A projectfactsheetproduced by the DoE says: “Successful implementation of this project could facilitate exploration of long-term CO₂utilization options, such as enhanced oil recovery, in the Southern Illinois Basin.”

Using the captured CO₂to extract previously out-of-reach oil reserves would temper the net emissions reductions achieved, according toyabo亚博体育app下载by theInternational Energy Agency．

Greenberg tells Carbon Brief that, while it would be a separate project from the current development, there was “potential” for the CO₂collected at the site to be used for enhanced oil recovery, if a pipeline were developed. “There are oil fields in southern Illinois, south of where this project is,” she tells Carbon Brief.

Meanwhile,several investigations, including one by亚慱官网, have raised doubts over the climate benefits of replacing fossil fuels with biomass.

Is it worth it?

This effort to install the world’s first BECCS facility is an important undertaking nonetheless. It is a chance to prove that it is feasible to acheive negative emissions.

This could potentially be scaled up in the future — geologistspredictthat the Mount Simon sandstone alone can hold between 27 to 109GtCO2, making it a potential resource for the Illinois Basin for several hundred years, where current emissions from point sources amount to 304Mt a year.

Apresentationby the DoE says that there is a large potential market for the technology in the US, with around 200 ethanol plants that have access to geological storage. Meanwhile,estimatesof CO2 storage capacity in the US range from 1,700 to 20,000Gt.

It is also an opportunity to win public support for the relatively unfamiliar idea of storing large amounts of CO2 underground, and ensuring that NIMBYs don’t become NUMBYs (“not under my backyard”), in thewordsof the DoE.

The project has spawned aNational Sequestration Education Centre, academicpaperson how to communicate the risks around CCS and acagey communication planthat includes a “no photo” policy and rules to restrict who speaks to the media to ensure “consistent messaging”.

Alone, the impact of the BECCS facilities at this ethanol plant may be negligible in terms of addressing global or even national emissions. Nonetheless, it is still the first large-scale demonstration of a technology that could prove vital to climate change efforts in the future.

主要形象:迪凯特设施as seen by Google Earth. Credit:Google Earth．