One important aspect of sustainability involves the life cycle of materials and energy extracted, consumed, transformed and disposed of in the functioning of urban societies.  Modern-day waste management should look at waste as a valuable resource, rather than simply bury or burn it. One promising technique is waste-to-energy (WTE) conversion, which offers an efficient means of managing waste commensurate to the needs of large population urban centers, while providing a source of alternative and renewable energy. San Mateo County’s sole landfill, Ox Mountain, is expected to reach capacity in only 14 years (by 2034). To achieve optimal waste energy management, it is key to link the circular economy framework (under which a restorative and regenerative economy takes a systematic approach to economic development designed to benefit businesses, society and the environment) to the waste-to-energy nexus framework (under which one utilizes reuse, reduction, recycling, recovery and reclamation techniques to address waste management, energy demand, and environmental concerns).

SMC has many innovative waste management pilot programs in place, including the Organics to Energy (O2E) Pilot Program and Stanford University’s Pilot Water Treatment Plants.

Photo Credit: here

Organics-to-Energy Pilot Program in San Mateo County

Even though most of San Mateo County’s residents understand the value of composting organic material either at home or placing it in the green bin for curbside pickup, participation rates are very low. Some organic waste even ends up as trash, creating an unnecessarily large volume of waste, which is becoming increasingly harder to handle.

The South Bay Waste Management Authority (SBWMA), branded as RethinkWaste and the Recology Center in San Carlos, is responsible for collecting, transporting and disposing of waste from homes and businesses. The cities where it operates in San Mateo County are Atherton, Belmont, Burlingame, East Palo Alto, Foster City, Hillsborough, Menlo Park, Redwood City, San Carlos and San Mateo.

SBWMA has initiated a pilot Organics-to-Energy (O2E) project to separate organic waste from trash. This initiative was undertaken even before California required that such steps be taken; the state now requires all jurisdictions to significantly reduce organics going to landfill where it produces and off-gasses methane, one of the worst greenhouse gases. The agency has purchased a $5 million extrusion press to remove organic material, convert it to a liquid slurry and transport it by trucks to wastewater treatment plants. At the plants, it will be dumped into anaerobic digesters for conversion to methane and then converted into energy. When completed, the project is projected to divert up to 200 tons of organic waste per day from landfills. The methane will be used to generate electricity and power engines at the wastewater plants, which, while still a combustion process and therefore a greenhouse gas contributor, will reprocess methane into clean energy.

Stanford University’s Pilot Anaerobic Water Treatment Plant

Funded by a $2 million California Energy Commission grant, Stanford University researchers collaborated with Silicon Valley Clean Water engineers to build and operate a small anaerobic water treatment plant in Redwood Shores. This pilot project is expected to operate through March 2021. It is cost-effective, with a potential savings of $2 million a year (compared to a traditional aerobic plant), and takes less physical space than an industrial-scale anaerobic plant (a 40% smaller footprint). It can digest pharmaceutical drugs and powerful household and industrial herbicides out of the waste stream, meaning that treated water could be used for “higher value” uses, including groundwater replenishment or in drip irrigation. In the long term, it could also be used for drinking.

The anaerobic wastewater treatment plant in Redwood Shores represents a fundamental shift in water treatment technology. Credit: Stanford.edu

 

Composting

San Mateo County’s Office of Sustainability created a website to educate residents about how to compost. This is an effective communication tool that simplifies conveying recycling, composting and waste guidelines to residents. RethinkWaste’s interactive website helps residents test their waste-management knowledge.

As part of its waste-energy management efforts, residents of 12 cities in the county receive CartSMART, a weekly curbside collection service for recycling, composting and trash once a week. The service is part of a 10-year contract (began in 2011) between Recology and RethinkWaste, also known as the South Bayside Waste Management Authority. The county’s Office of Sustainability also runs a community garden partnerships program that partners with local community organizations and businesses to build vibrant community gardens and promote sustainable composting techniques.

Composting helps keep organic waste from ending up at Ox Mountain, San Mateo County’s sole landfill, which is near capacity. One such partnership is Compost Hub, a community compost network. Residents are able to bring their food scraps to the weekly farmers market located in East Palo Alto in exchange for vouchers to use at the farmers market. Additionally, residents receive free access to education workshops and free airtight bins that they can place under their sinks. Image credit.

The Recology team works with businesses and community partners to implement new recycling programs or improve existing programs. The team help partners apply best management practices for recycling and composting items that are eligible, to keep them out of the landfill. A prime example is the Promontory Point apartment complex, located in Foster City. It is a multifamily dwelling with 90 units, totaling three separate buildings. The Recology team found that 30% of residents’ organic waste was being placed in landfill carts. It recommended implementing and increasing organics services and decreasing garbage service by providing more green composting bins and decreasing the number of black trash bins. Image Source.

COVID-19’s Impact on Waste Management

On March 18, 2020, San Mateo County issued health orders, shelter-in-place ordinances and social distancing protocols designed to mitigate the COVID-19 pandemic. Although the full impact of these new policies has not been fully studied yet, below are a few observable, immediate impacts on waste management:

  • The RethinkWaste facility continues to receive waste during COVID-19. Residential waste generation continues, but commercial and development waste generation has drastically declined.
  • Residential customers increased recycling during the shelter-in-place period, and RethinkWaste was able to upgrade its machinery and technology during this time.
  • The O2E Program has been delayed as the needed volume to run the program is not met by residential food waste only and depends heavily on local merchants’ food waste volumes.[1]
  • Reusable bags for grocery shopping were banned temporarily, leading to an increase of plastic bag usage. Personal Protective Equipment (PPE) such as gloves, masks, and wipes must be thrown away for health and safety reasons; these items cannot be recycled as they may contaminate the recycling stream and threaten the health and safety of workers at recycling facilities. As PPE is recommended for all individuals who need to work or go outside of their home, the amount of PPE being thrown away and headed to landfills is high.

An emerging topic in waste-to-energy management is anaerobic food waste digestion. Anaerobic digestion occurs naturally, in the absence of oxygen, as bacteria break down organic materials and produce biogas, which can then be used as an energy source. Some research indicates that optimal waste management systems pair an anaerobic food waste system with a composting system.[2][3] The EPA suggests that shifting to a solely anaerobic food-waste system is most effective and cites major benefits from such a system to the economy and to climate change mitigation efforts. Click here to learn more about anaerobic digestion and see a comparison with composting.

Photo Credit: Renergy

References

[1] Lopez, Sierra. “San Mateo County Solid Waste Habits May Hold Signs for Potential Economic Recovery.” The Daily Journal, 7 July 2020, www.smdailyjournal.com/news/local/san-mateo-county-solid-waste-habits-may-hold-signs-for-potential-economic-recovery/article_d2229f68-c001-11ea-9714-97a534e669c3.html.

[2] Kraemer, Tom, and Scott Gamble. “Integrating Anaerobic Digestion With Composting.” BioCycle, Nov. 2014, www.biocycle.net/integrating-anaerobic-digestion-with-composting/

[3] Karidis, Arlene. “Why Co-Locate Compost and Anaerobic Digestion?” Waste360, 27 Nov. 2018, www.waste360.com/business-operations/why-co-locate-compost-and-anaerobic-digestion