Green Infrastructure

Urban grey infrastructure, used to move stormwater, is often single-purposed, aged, and is costly to maintain.
Green infrastructure is a nature-based solution that filters and contains stormwater at the source.

Current Water Management Practices

Heavy rainfalls often overwhelm municipal sewer systems and overflow onto city streets, consequently carrying many contaminants such as bacteria, heavy metals, and trash. These organic and inorganic pollutants pose a threat to the environment and the health of the population. Current urban water management systems involve grey infrastructure such as pipes, gutters, and detention tanks that can contain and move effluent away from communities. As these systems become aged and overburdened, they become less efficient and more expensive to maintain.

Urban Compaction

The hardscapes of urban infrastructure make it difficult for vegetation to reach its full potential. The soil is often compacted to structurally support human traffic as well as loads and often lacks valuable nutrients in their isolated plots. This consequently leads to poor water retention during heavy rains, low survival rate of street trees, and poor long term soil health.

Biocarbon for Green Infrastructure

Biocarbon (or biochar) is produced from a wide variety of organic feedstock, ranging from lignocellulosic materials to nutrient rich waste streams such as food waste. Biocarbon produced through the thermochemical conversion of organic waste and agricultural residue has valuable properties such as high surface area and large number of pores, that present a valuable medium towards green infrastructure.

The many voids in biocarbon serve as pockets to absorb and retain moisture and nutrients longer to ensure long-term plant availability. It is well suited to bioretention green infrastructure systems to help boost the water retaining abilities of the soil and consequently lead to thriving flora in these systems. Biocarbon also aids in preventing complete nutrient washout during heavy storms.

Green Infrastructure

Green infrastructure are systems that incorporate the abilities of flora to filter contaminants and contain stormwater runoff at the source. This helps to reduce the volume of water that overwhelms municipal sewers and allows for groundwater recharge through deep percolation. Examples of green infrastructure include green roofs, rainwater harvesting, urban tree canopies, permeable pavements, rain gardens and planter boxes, bioswales, constructed wetlands and land conservation, and structural soils.

Structural Soils

Structural soils are composed of macadam, a blend of gravel of various sizes and smaller soil amendments like peat, sand, clay, and lava, and biocarbon. This layout is successful in improving tree health and longevity by providing voids for the roots to expand through. In turn, healthier and stronger trees can grow in street planters so that more carbon could be drawn down by them and more water could be held in the ground.

Case Study: Stockholm Biochar Project

An example of an outstanding application of biocarbon in green infrastructure is in Stockholm, Sweden where trees were withering due to the lack of space and nutrients for root development. Tree Officer Bjorn Embrén and his team skillfully piloted the Stockholm Biochar Solution to drastically improve the lives of many of the city’s trees by reconstructing the tree planters using structural soils with the assistance of biocarbon. This project was also supported by the citizens of Stockholm as they were encouraged to bring waste from their gardens to create biocarbon with. In return, the citizens were given biocarbon to improve the yields of their own garden.

Additional co-products of the pyrolysis process include pyrolysis oil as well as synthetic gas that can be used to generate energy for heating and electricity for the city. The Stockholm Biochar Solution has inspired many other cities around the world such as Helsingborg, Chicago, and Minneapolis to pursue their own similar projects in their municipalities.