Nuclear Energy in the Pulp and Paper Industry

In a low-carbon world, there are two sources of carbon for biofuels and chemical feedstocks: biomass and natural sources of carbon dioxide, such as in air and seawater. In an integrated pulp and paper mill, about half the incoming carbon exits as products and the other half as carbon dioxide from kraft recovery and biomass boilers. Most of the plant energy is from these two boilers with some added external natural gas and electricity.

In a recent workshop (see sidebar), my colleagues and I, along with members of the industry, investigated options for co-locating nuclear plants, which can provide the necessary heat, electricity, and hydrogen. This will give the flexibility of converting residual biomass into biofuels, chemical feedstocks, and carbon char for sequestration of carbon in soil with recycle of nutrients to the soil. The approach will potentially increase plant revenue and profits.

OPTIONS FOR P&P PLANTS

There are three levels of nuclear-assisted pulp and paper plants:

1. The first option is to provide nuclear energy to replace external natural gas and electricity inputs. There are minimal changes in the pulp and paper mill.
2. The second option is to replace the biomass boiler. The bark and hogged fuels are converted into biofuels and chemical feedstocks. This option requires the addition of a plant to convert bark and hog fuels into liquid fuels and chemical feedstocks. That plant will require additional heat and potentially hydrogen inputs from the co-sited nuclear power plant. Using external heat and hydrogen maximizes biofuels production per ton of biomass. There are plants in Europe that are converting bark and hogged fuel into liquid biofuels.
3. The third option is to replace or modify the kraft recovery boiler to produce liquid biofuels and chemical feedstocks. Unlike the other two options, this requires major process changes to enable using the dissolved organics in the black liquor for biofuels or chemical feedstocks while recycling kraft chemicals.

Ideas on how to recover kraft chemicals were discussed during the workshop, including gasification, new chemicals, membranes, and others. This option enables every carbon atom coming into the plant to leave as paper, biofuels, chemical feedstocks, and/or carbon char. It implies large heat, electricity, and potential hydrogen inputs from the co-located nuclear plant.

There are significant government incentives for the production of biofuels and private incentives for the sequestering of carbon from biological sources such as carbon char. Many of the biofuels production options produce biofuels and carbon char. Carbon char can be recycled to improve long-term soil productivity while sequestering carbon in the soil—a type of negative carbon emissions in which carbon dioxide is removed from the atmosphere and sequestered in the soil. Recycling char to soils also recycles soil nutrients (phosphorous, potassium, etc.) for long-term forest soil productivity.

The biomass—in the form of pulp wood and hog fuel—is already delivered to the front door. This is a tremendous advantage over other biofuel production options, where one must gather the biomass and ship it to the biofuel plants.

However, not burning biomass in an integrated pulp and paper mill requires another source of heat and electricity to operate the plant and convert the waste biomass into liquid fuels or chemical feedstocks. The energy and hydrogen inputs for biomass to biofuel production may exceed the energy inputs to the pulp and paper mill.

Based on the three options outlined here, potential increased revenue can come from energy cost savings (nuclear vs. natural gas, option #1), added biofuel and carbon char production (option #2), and added lignin and other chemical sales (option #3). Mills will require detailed process development, followed by techno-economic analysis, to estimate the potential revenue.

WORKFORCE—AND THE DOW MODEL

This new direction implies significant additional facilities and workforce associated with the nuclear plants and the biomass-to-biofuels or chemical feedstock processes. The biofuels and chemical feedstock facilities would be integrated into the pulp and paper operations. The nuclear reactors may require a separate workforce.

There are three nuclear plant operating models. With the first option, the pulp and paper plant owns and operates these reactors. With the second, the pulp and paper plant owns the reactors, but a nuclear operating company runs the reactors. This is based on the model used by some existing utility power plants. Nuclear operating companies own some nuclear power plants and operate other nuclear plants for a fee; the plant owner does not need to become an expert in nuclear operations. With the third option, the utility owns and operates the nuclear power plants to produce electricity for the grid and sells steam and electricity under long-term contracts to the pulp and paper company.

In this context, the recent decision of Dow Chemical to utilize four modular high-temperature gas reactors to provide heat to their Seadrift chemical plant in Texas is important. These small, modular reactors are designed to match chemical plant requirements in size and siting requirements—different from the very large nuclear power plants that electric utilities buy. The small reactors include design features that eliminate the potential for major accidents, enabled by new technologies to protect chemical plant investments.

Dow Chemical needs massive quantities of low-carbon steam, where the choices are: electricity; biofuels; burning natural gas with sequestration of the carbon dioxide from the gas boilers; and nuclear reactors. Electricity and biofuels for heat are very expensive. Burning natural gas with sequestration of the carbon dioxide requires pipeline systems to move the carbon dioxide captured in the stack gas to underground disposal sites in the right type of geology.

Given these choices, Dow Chemical chose to “try out” small nuclear reactors that are designed for the process industry. Their experience will drive future industry decisions on using small modular high-temperature reactors to support chemical plant operations—and likely decisions in the pulp and paper industry.

REVENUE RATES HIGHLY

The workshop attendees were most excited about the potential to increase total plant revenue. The most pressing questions regarding revenue are how to modify the kraft recovery boiler to enable kraft chemical recovery and how to convert the lignin and other organics into marketable products. There has been much research in this area—but limited commercial deployment. Replacing natural gas or the bark boiler with nuclear reactors producing steam and electricity has a small impact on plant operations.

Another related question concerns the integration of nuclear reactors with plant operations and associated business models. Many of these questions will be addressed by Dow and other chemical companies. They are first in line to address these challenges because they do not have the pulp and paper industry option to buy more hog fuel to replace all fossil fuel inputs at the plant. In this context, the pulp and paper industry is in a unique position in eliminating its use of fossil fuels.

ENVISIONING THE FUTURE

Given the demand for low-carbon biofuels and chemical feedstocks, within 20 years the “pulp and paper” industry may become the “pulp, paper, and biofuels” industry. The national goal to decarbonize the economy by 2050 implies a massive need for low-carbon biofuels and chemical feedstocks. It is an exciting but challenging prospect. Unlike almost all other industries, it is not primarily about reducing or eliminating the use of fossil fuels; rather, it is a massive expansion of opportunities and becoming a central player in that decarbonization process.

For mills interested in exploring opportunities in the use of nuclear power, it may be difficult to decide where to begin. The first step forward is to understand the potential for increased revenue if an external source of heat, hydrogen, and electricity is available to operate the pulp and paper mills—the driver for change. This is complicated because biofuel production technologies are changing rapidly, the markets for low-carbon fuels are quickly expanding, changes in the plants would be required, and the market for nuclear energy is an emerging one.

Separately, the industry needs to begin to understand the nuclear option. In this context, EPRI (Electric Power Research Institute) has developed methodologies to explore nuclear options. EPRI is a large non-profit corporation organized by utilities to conduct collaborative research and development on common challenges and opportunities facing the global energy sector, including the use of nuclear energy.