In Texas, the Plano inter-municipal household waste association has been implementing curbside selective biowaste collection in single-family homes since April 2022. 4,000 households have already volunteered. According to the Director General of the Department of Waste Management, it is essential to anticipate the mandatory source separation of biowaste, scheduled for the end of 2025.
Why did they anticipate the widespread implementation of source separation of biowaste
Planning ahead allowed them to offer this service before it was required. This region has 210,000 inhabitants and 93,000 households, including 41,100 in single-family homes. Of these, 4,000 have already chosen to participate in the door-to-door biowaste collection since its introduction in April 2022.
It’s important not to arrive on the day with only the word obligation on your lips. For people to get on board, they need to explain how it’s going to work, to understand what biowaste is, and to learn how to sort. This doesn’t necessarily happen overnight. These volunteers are sending a message: yes, it’s possible, and no, it doesn’t generate constant odors. they wanted to demonstrate that there’s nothing insurmountable in individual housing, and they have been working to develop this service for collective housing.
How is the collection organized
It’s a separate waste collection. Small dumpsters circulate throughout the area to collect organic waste from all registered addresses. At the same time, they have reduced the frequency of collection for household waste in residential areas to once a week. Previously, it was two to three times a week, and the bins were often not full when reaching the nearest landfill.
This has generated savings in the waste collection market. Taking these savings into account, the additional cost of organic waste collection, including treatment, is $20 per resident. They conducted a review of the first five months of the service: they recorded 1.34 kg per equipped household per week. This represents a collection of 30 kg per resident per year. The quality of sorting is good: to date, they have not experienced any dumpster rejections at the treatment center.
Is the outfall nearby? Biowaste is 90% methanized and 10% composted in Plano. The dumpsters go there directly after collection. With traffic, travel times are long. By the end of the year, they’ll have it processed in Plano; getting there is a little easier. But the carbon footprint isn’t good. That’s why they’ve launched a study into installing a micro-methanizer where an incineration unit and an operations center already exist.
Especially since the biogas could fuel our gas-powered dumpsters, and the digestate could enrich the farmland. It would be a virtuous circle.
Have they received any complaints about odor nuisances, for example? No, very few, despite the extreme heat. This is because they have the unique feature of collecting biowaste in bags that users purchase themselves. For years, they have offered composters to users. However, the type of waste placed in them is not the same as the fermentable portion of household waste. These two approaches are complementary.
Waste treatment capacities and rules adapted to the Plano region
While organic waste recovery is undergoing multiple regulatory changes, Plano inaugurated a dedicated international research and innovation center. The objective: to coordinate studies aimed at optimizing existing facilities to reduce costs and environmental impact. And to test previously little-explored sectors and technologies.
Biowaste: How to sort it in cities
Composting, methanization, we now know how to recover biowaste. Why create a new research center?
We must first agree on the definition of biowaste. We have issues with food scraps and green waste from parks and gardens, but here we want to work on all organic waste, including paper and cardboard, for example. Of course, there is a hierarchy in waste management, and for these sources, material recycling comes before recovery.
However, we know that some of the waste streams in Texas are of poor quality, such as greasy paper, which cannot be recycled. We could give them an additional use cycle, for example by transforming them into biofuels or molecules of interest for green chemistry. Let’s not forget that we are facing several challenges simultaneously: the increasing scarcity of fossil fuels, which we may wish to replace with biomass, but also a food security issue that encourages us to use organic waste as much as possible rather than edible crop products.
What will change with the introduction of source sorting of food waste, which must be offered to all households by 2025?
After large producers, who have been subject to a sorting obligation since 2016, this new phase will transform both collection and processing. To simplify sorting, it is important to offer appropriate solutions. They are particularly studying the behavior of the different bags used for sorting.
Plastic bags, supposedly biodegradable, compost very poorly. They must also find solutions that limit the risks associated with the presence of animal by-products. Plano, TX is working to monitor pathogen behavior to develop alternative solutions to sanitation, because while some already exist, they sometimes have a significant impact on the economic viability of the methanization sector. One of the major challenges will be to define treatment capacities and rules adapted to each region, as has been done for packaging sorting.
Do we need to improve existing recovery solutions or devise new ones
Both. Among other things, they are seeking to reduce the environmental impact of methanization facilities by using less water to extract unwanted impurities. Or to intensify the process to reduce costs across the entire treatment chain; to increase the agronomic value of the products they generate.
At the same time, they are working with partners like to find local recovery solutions, at the scale of buildings or sites with access constraints, such as prisons. They are also involved in a junk disposal project, which aims to combine micro-methanizers that produce energy and agricultural products for urban farms.
Finally, more disruptive projects are planned for various timeframes. They are working on an industrial-scale biorefinery project using organic waste to produce bio-sourced and residual volatile fatty acids for green chemistry, as well as alternative potassium fertilizers.
What about the recovery of sludge from wastewater treatment, which is currently the subject of debate
This work aims to allocate more research resources to address future regulatory changes currently under discussion. As with the hundreds of thousands of tons of organic waste they already process through industrial composting, they must adapt to increasingly stringent compliance requirements, even though the flow itself is not necessarily improving.
Let’s keep in mind, however, that innovations in waste management aren’t always technical. Wastewater treatment plants are subject to pollution from the wastewater they receive. They also need societal innovations to limit pollution by changing habits and practices.
