Plant-based food alternatives could support a shift to global sustainability

Replacing 50% of meat and milk products with plant-based alternatives by 2050 can reduce agriculture and land use related greenhouse gas (GHG) emissions by 31% and halt the degradation of forest and natural land, according to new research.

According to the study just published in Nature Communications, additional climate and biodiversity benefits could accrue from reforesting land spared from livestock production when meat and milk products are substituted by plant-based alternatives, more than doubling the climate benefits and halving future declines of ecosystem integrity by 2050. The restored area could contribute up to 25% of the estimated global land restoration needs under Target 2 of the Kunming Montreal Global Biodiversity Framework by 2030.

The study is the first to look at the global food security and environmental impacts of plant-based meat and milk consumption at large scales that considers the complexity of food systems. The research was conducted independently by IIASA in partnership with the Alliance of Bioversity and CIAT, as well as USAID, and solicited input from Impossible Foods -- a company that develops plant-based substitutes for meat products -- as a potential user of the data to ensure relevance. The company also provided generic recipes for the plant-based meat substitute products used in the analysis. The data are, however, not specific to Impossible Foods and the science team had complete control over decision making.

"Understanding the impacts of dietary shifts expands our options for reducing GHG emissions. Shifting diets could also yield huge improvements for biodiversity," notes study lead author Marta Kozicka, a researcher in the IIASA Biodiversity and Natural Resources Program.

"Plant-based meats are not just a novel food product, but a critical opportunity for achieving food security and climate goals while also achieving health and biodiversity objectives worldwide. Yet, such transitions are challenging and require a range of technological innovations and policy interventions," adds study coauthor Eva Wollenberg from Alliance of Bioversity International and CIAT and the Gund Institute, University of Vermont.

The authors developed scenarios of dietary changes based on plant-based recipes for beef, pork, chicken, and milk. The recipes were designed to be nutritionally equivalent to the original animal-derived protein products and realistic for the existing food manufacturing capabilities and globally available production ingredients (Fig 1).

The authors found that a 50% substitution scenario would substantially reduce the mounting impacts of food systems on the natural environment by 2050 compared to the reference scenario (Fig 2). The impacts as compared to 2020 include:

• Global agricultural area declines by 12% instead of expanding.
• The decline in areas of forest and other natural land is almost completely halted.
• Nitrogen inputs to cropland are nearly half of the projections.
• Water use declines by 10% instead of increasing.
• Without accounting for any carbon sequestration on spared land, GHG emissions could decline by 2.1 Gt CO2eq year-1 (31%) in 2050 (1.6 Gt CO2eq year-1 on average in 2020-2050).
• Undernourishment globally declines to 3.6%, as compared to 3.8% in the reference scenario (reducing the number of undernourished people by 31 million).

The full environmental benefit of diet shifts can be achieved if the agricultural land spared from livestock and feed production is restored through biodiversity-minded afforestation. In the 50% scenario, the benefits from reduced land-use emissions could double as compared to a scenario without afforestation -- a total reduction of 6.3 Gt CO2eq year-1. At 90% substitution, the reduction of all agriculture and land-use emissions would increase to 11.1 Gt CO2eq year-1 in 2050.

The restoration of forest ecosystems would also improve biodiversity. The 50% scenario would reduce predicted declines in ecosystem integrity by more than half, while the 90% scenario could reverse biodiversity loss between 2030 and 2040.

"While the analyzed dietary shifts serve as a powerful enabler for reaching climate and biodiversity goals, they must be accompanied by targeted production side policies to deliver their full potential. Otherwise, these benefits will be partly lost due to production extensification and resulting GHG and land-use efficiency losses," explains IIASA Biodiversity and Natural Resources Program Director Petr Havlík, who coordinated the study.

The study points out that impacts across regions could differ due to differences in population size and diets, unequal agricultural productivity, and participation in international trade of agricultural commodities. The main impacts on agricultural input use are in China and on environmental outcomes in Sub-Saharan Africa and South America. These regional differences could also be used to design better interventions.

"A global introduction of all novel alternatives has additional benefits compared to the scenarios with limited product or geographical scope, but regional substitution of specific products may be highly effective, especially if combined with regional strategies and purposeful selection of recipes," Kozicka explains.

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Colorful films could help buildings, cars keep their cool

The cold blast of an air conditioner can be a welcome relief as temperatures soar, but "A/C" units require large amounts of energy and can leak potent greenhouse gases. Today, scientists report an eco-friendly alternative -- a plant-based film that gets cooler when exposed to sunlight and comes in a variety of textures and bright, iridescent colors. The material could someday keep buildings, cars and other structures cool without requiring external power.

The researchers will present their results at the spring meeting of the American Chemical Society (ACS).

"To make materials that remain cooler than the air around them during the day, you need something that reflects a lot of solar light and doesn't absorb it, which would transform energy from the light into heat," says Silvia Vignolini, Ph.D., the project's principal investigator. "There are only a few materials that have this property, and adding color pigments would typically undo their cooling effects," Vignolini adds.

Passive daytime radiative cooling (PDRC) is the ability of a surface to emit its own heat into space without it being absorbed by the air or atmosphere. The result is a surface that, without using any electrical power, can become several degrees colder than the air around it. When used on buildings or other structures, materials that promote this effect can help limit the use of air conditioning and other power-intensive cooling methods.

Some paints and films currently in development can achieve PDRC, but most of them are white or have a mirrored finish, says Qingchen Shen, Ph.D., who is presenting the work at the meeting. Both Vignolini and Shen are at Cambridge University (U.K.). But a building owner who wanted to use a blue-colored PDRC paint would be out of luck -- colored pigments, by definition, absorb specific wavelengths of sunlight and only reflect the colors we see, causing undesirable warming effects in the process.

But there's a way to achieve color without the use of pigments. Soap bubbles, for example, show a prism of different colors on their surfaces. These colors result from the way light interacts with differing thicknesses of the bubble's film, a phenomenon called structural color. Part of Vignolini's research focuses on identifying the causes behind different types of structural colors in nature. In one case, her group found that cellulose nanocrystals (CNCs), which are derived from the cellulose found in plants, could be made into iridescent, colorful films without any added pigment.

As it turns out, cellulose is also one of the few naturally occurring materials that can promote PDRC. Vignolini learned this after hearing a talk from the first researchers to have created a cooling film material. "I thought wow, this is really amazing, and I never really thought cellulose could do this."

In recent work, Shen and Vignolini layered colorful CNC materials with a white-colored material made from ethyl cellulose, producing a colorful bi-layered PDRC film. They made films with vibrant blue, green and red colors that, when placed under sunlight, were an average of nearly 40 F cooler than the surrounding air. A square meter of the film generated over 120 Watts of cooling power, rivaling many types of residential air conditioners. The most challenging aspect of this research, Shen says, was finding a way to make the two layers stick together -- on their own, the CNC films were brittle, and the ethyl cellulose layer had to be plasma-treated to get good adhesion. The result, however, was films that were robust and could be prepared several meters at a time in a standard manufacturing line.

Since creating these first films, the researchers have been improving their aesthetic appearance. Using a method modified from approaches previously explored by the group, they're making cellulose-based cooling films that are glittery and colorful. They've also adjusted the ethyl cellulose film to have different textures, like the differences between types of wood finishes used in architecture and interior design, says Shen. These changes would give people more options when incorporating PDRC effects in their homes, businesses, cars and other structures.

The researchers now plan to find ways they can make their films even more functional. According to Shen, CNC materials can be used as sensors to detect environmental pollutants or weather changes, which could be useful if combined with the cooling power of their CNC-ethyl cellulose films. For example, a cobalt-colored PDRC on a building façade in a car-dense, urban area could someday keep the building cool and incorporate detectors that would alert officials to higher levels of smog-causing molecules in the air.

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