State of the Planet

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We Need to Advance Solid Waste Technology

New York City is gradually rolling out food waste recycling, and that is long overdue. The technology of anaerobic digestion and composting is known and available. We should do all we can to use current technology to recycle as much as we can: especially food waste, aluminum, and rare earth metals that have a market value and are cost-effective to recycle today. But the reasons that various recycling efforts have often faltered are (1.) the difficulty of assuring a “clean” waste stream uncontaminated with materials that don’t belong, (2.) the uncertain market for recycled materials, and (3.) the cost of multiple garbage pickups.

In the United States, more and more of our garbage is “treated” rather than landfilled, but America still has a massive problem with solid waste production and disposal. According to the EPA:

“Over the last few decades, the generation and management of MSW [municipal solid waste or garbage] has changed substantially. Generation of MSW increased … from 88.1 million tons in 1960 to 292.4 million tons in 2018… The generation rate in 1960 was just 2.68 pounds per person per day. It increased to 3.66 pounds per person per day in 1980. In 2000, it reached 4.74 pounds per person per day and then decreased to 4.69 pounds per person per day in 2005. The generation rate was 4.9 pounds per person per day in 2018, an 8 percent increase from 2017…Over time, recycling and composting rates have increased from just over 6 percent of MSW generated in 1960 to about 10 percent in 1980, to 16 percent in 1990, to about 29 percent in 2000, and to about 35 percent in 2017…Landfilling of waste has decreased from 94 percent of the amount generated in 1960 to 50 percent of the amount generated in 2018.”

Garbage must be collected and then brought to a facility of some kind to be treated, burned, or dumped. As our population has grown and consumption has grown, so too has our garbage. While per-capita production waste seems to have stabilized, it represents a huge amount of material, and it is essential that we figure out how to reuse it. Recycling is a great tool of environmental education, and it does help divert waste from landfills, but it is not going to bring us close to a circular economy. To implement a true circular economy, we need to systematically and automatically reuse most of the material placed in our trash bags. In my new book, Environmentally Sustainable Growth, I discuss the idea of mining resources from a single mixed waste stream. As I wrote in that book:

“The solution to waste management will rely on new technologies. One of the most promising of these allows the collection of a single waste stream and then mechanically separates the garbage. With artificial intelligence (AI) and automation, we can expect this infrastructure to become operational and cost effective over the next decade. Today some of the sorted waste goes to an anaerobic digester, some is recycled, some is burned for energy, and the residue of the incinerated garbage can be used as construction material. However, we can expect advances in sorting infrastructure.

The specific infrastructure advances needed would include waste-sorting plants to separate food, plastics, paper, metals, and chemicals, and then sending these clean waste streams to reprocessing plants. These plants will be the logical connection points to a true circular economy. While some American cities have very low waste management costs, all of them pay to collect and dispose of waste. Those costs can be shifted to a system that, instead of dumping and burning waste, will sort and sell raw materials such as plastic feedstock, paper, and the chemical components of fertilizer. These reclaimed raw materials could pay for some of the costs of disposal in the future. But the cost of this sophisticated system of waste management will be large, and in its initial stages, it will require federal subsidies for research, pilot projects, and the cost of capital.”

This type of technology is not a fairy tale: elements of it are already being tested, and some are in actual use. Jason Calaiaro, former head of engineering* at Amp Robotics in Louisville, Colorado, explains how his company’s AI-based system works in an article in IEEE Spectrum. According to Calaiaro, his company:

“…is developing hardware and software that relies on image analysis to sort recyclables with far higher accuracy and recovery rates than are typical for conventional systems. Other companies are similarly working to apply AI and robotics to recycling, including Bulk Handling Systems, Machinex, and Tomra. To date, the technology has been installed in hundreds of sorting facilities around the world. Expanding its use will prevent waste and help the environment by keeping recyclables out of landfills and making them easier to reprocess and reuse.”

In Italy, IBM is working with Hera, that nation’s largest waste management and recycling company to use video and AI to enhance waste separation and recycling. Academic literature on elements of automated waste management systems is becoming more common. A recent (2022) article by Pravin R. Kshirsagar et al. is entitled “Artificial Intelligence-Based Robotic Technique for Reusable Waste Materials.” This article reported a study that identified:

“…the steps that must be taken to maximize the use of garbage. This work describes a reusable industrial robot arm for grasping and sorting things depending on the resources they contain. Gripping, motion control, and object material categorization are all integrated into a full-automation, reusable system architecture in this study… Movement in terms of moving the robot in the most efficient way possible, the robot’s grabbing, and categorization were incorporated into the movement design process.”

When the waste management system includes electric vehicles and is powered by renewable energy augmented by waste-to-energy generation of electricity, elements of the circular, renewable resource-based economy can move beyond theory into operational reality. The goal should be to replace the mining of natural resources from the earth with the mining of the waste stream. The business model holds promise due to the rising cost of waste collection and disposal and the increased scarcity of some critical natural resources. Aluminum recycling is already less expensive than manufacturing aluminum from raw materials.

While the economics of waste mining holds promise, as in most new technologies, the financial risk of developing the technology is far from trivial. Additionally, we face the difficulty of overcoming institutional inertia to replace current practices with new ones. Sanitation departments are not known for their willing embrace of new technologies and waste management techniques. Moreover, elected officials do not see much upside in trying to solve garbage problems. No mayor is eager to cut the ribbon at a new waste management facility. Finally, new technology will require new waste management facilities, and few neighborhoods are eager to be the site of those facilities.

The technologies themselves are still under development, and the U.S. federal government might consider funding engineering and management studies to accelerate the development of automated waste management and mining technologies. Given the number of private corporations already working in this area, tax credits might also be used to encourage efforts to develop public-private partnerships between cities, regions, states, and private waste management firms. Attracting private capital and investment in new waste facilities may initially require either tax breaks or direct government investment. Cities like New York have the scale needed to invest their own capital budget in building an advanced waste management facility. If a modern New York City waste facility needed to be located outside of the city, a waterfront town (to enable barging waste) might be offered low-cost access to the facility to reduce their own costs of waste management.

While advanced waste management is essential to urban sustainability, it would require a visionary public leader to see the need for innovation, and it would take a highly skilled political communicator to turn the waste issue into something besides the losing issue it has typically been. As mining the planet becomes more destructive and more expensive, I believe the need for waste mining will become clearer. By then, the technology may well be more proven, and the revolution in waste management we need could become a reality.

*Editor’s note: A previous version of this story stated that Calaiaro is president of AMP Robotics. The statement was corrected on April 4, 2023 at 9:25am.

Views and opinions expressed here are those of the authors, and do not necessarily reflect the official position of the Columbia Climate School, Earth Institute or Columbia University.

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