Can paper waste be used to make black ink?

In brief:

Project:
“Waste Paper Derived Biochar for Sustainable Printing Products”

Focus:
Circular applications of biochar as an industrial material  

Type of research:
Material science  

Lead Researcher:
Dr. Thomas Trabold, Department Head, Department of Sustainability, Golisano Institute for Sustainability, Rochester Institute of Technology

Quick look:

• Black-ink manufacturing contributes to climate change. The black ink commonly used in pens, home inkjet and laser printers, newspapers, books, and more is derived from the thermal decomposition or partial combustion of fossil fuels.
• Thomas Trabold (GIS) has developed a method for using post-consumer paper to make a highly sustainable black ink.
• Trabold’s work applies biochar (pyrolyzed biomass) as an elemental carbon to replace the use of carbon black in black-ink production. It paves a way for decoupling black-ink production from fossil fuels and sequestering carbon captured by trees into a stable state.
• The result of this study is a sustainable black-ink pigment made from biochar with strong market potential. Capturing even 1% of the global printing sector would be worth $200 million in sales.

The research:

Climate scientists expect the global temperature to exceed the threshold target set at the 2015 Paris Agreement of 1.5 degrees—fast innovation for sustainable industrial materials has become critical. It’s with this urgency in mind that Dr. Trabold and his research team launched a study in 2017 to determine whether biochar made from waste paper could be used to produce a black-ink pigment for consumer and commercial printing (e.g. inkjet, lithography, and flexography).

Conventional black-ink pigment is made from coal black, an industrial product first discovered in the nineteenth century that is made through the incomplete combustion of heavy petroleum or natural gas. It is also used as a reinforcing filler in automobile tires, rubber products, and also as a coloring additive in plastics and paints. Dr. Trabold’s supplemental work to this project found that biochar, as an elemental carbon, has many of the same performance properties of carbon black, which led him to consider it as a promising substitute.

Biochar is a fine-grained residue derived from thermochemically treating organic biomass (a process known as a pyrolysis). It is most commonly used to improve soil health in agriculture, and, until now, little research has focused on its potential as an industrial additive.

Not only would a bio-char-based ink pigment provide an alternative to fossil-fuel ingredients, but it would also offer a practical economic incentive for carbon sequestration. That’s because pyrolysis, as a thermal conversion process that occurs in an environment where oxygen is absent, produces a small amount of carbon dioxide (CO₂). Without oxygen molecules in the air, carbon molecules remain mostly in the solid state. Making biochar from postconsumer paper waste means that the carbon that trees remove from the atmosphere can be put into a reliable and stable form. So, while biochar replaces fossil-fuel-based carbon black in ink, it’s also safely removing tons of carbon out of the air.

Dr. Trabold designed the study with the understanding that an ink pigment made from paper-waste biochar would quickly meet a demand for more sustainable products in the global printing-ink market, which is forecasted to reach $23.8 billion by 2023. That means a market share of just 1% could deliver more than $200 million in sales.  

Biochar has conventionally been used to process freely available or low-cost waste, and paper would be no exception. Prior research in this area has shown that biochar can be made from a wide range of paper products, including box cardboard, paper towels, and glossy paper. Disposing of or recycling these materials can be costly for businesses, so reorientating their value as commodities opens a new, circular economic opportunity.   

Study results:

Dr. Trabold’s exploration of biochar is an example of how material science can be applied to mitigate the causes of climate change while charting new pathways for economic prosperity.

New, sustainable ink developed

The project was successfully conducted in collaboration with Dr. Scott Williams’ research group in RIT’s School of Chemistry and Materials Science. The team created a new category of sustainable black ink made entirely from finely ground waste-paper biochar pigments. Testing using an oil-based, manual letterpress produced high-quality images at a 30% pigment loading rate (compared to the average 4–8% rate for traditional inks).

An effective carbon-sequestration method

The researchers evaluated paper waste flows at a Staples distribution center as part of the study. They found that the annual amount of waste created could be converted into about 200 metric tons of biochar, which would sequester nearly 330 metric tons of carbon dioxide equivalent (CO_2e). This would produce enough pigment for about one million liters of biochar ink (based on an 8% loading rate).

Challenge to large-scale production

Scaling up production of the biochar ink for the multi-billion dollar commercial printing market would mean addressing a substantial challenge. The particle size of the biochar ink developed in the study was larger than the average size of a coal-black pigment particle (∼20μm, compared to ∼0.5μm). An inverse relationship exists between particle size and the depth of black hue. While this can be remedied by further grinding of the biochar pigment, it negatively impacts its overall cost-efficiency and, subsequently, the economic feasibility of the product.

Inorganics in feedstock affect quality

When paper feedstock included high levels of inorganic additives like kaolin clay, titanium dioxide (TiO2) or calcium (Ca), further processing was required to ensure optimal quality. This can be costly.

Looking ahead:

Biochar can be made from nearly every kind of organic material, including plant- and animal-based food waste. It opens an economically productive pathway for diverting major drivers of climate change into sustainable uses. Even if biochar inks cannot replicate the quality of inks made from fossil fuels in every instance, there may be unique applications where it meets product specifications as a sustainable alternative. This may include printing on boxes and other packaging materials. In fact, using post-consumer box cardboard to create biochar ink for printing on boxes is a circular-economy model that many companies are considering.

Following this study, Dr. Trabold is continuing to explore industrial applications of biochar made from organic materials, including food waste. He has recently engaged in a project to evaluate the performance of biochar–bioplastic composites for use in agriculture. 

See the journal paper that was published in 2021 after additional research ›

See all work by Dr. Trabold ›