While recent electoral outcomes may spur an underground resistance movement, climate change is the common culprit for undergrounding; i.e. moving electric, telephone and internet cables from above ground to below it. Not only does undergrounding improve aesthetics and property values, but it increases reliability, resilience and safety. Downed power lines from natural disasters or power line failures have led to massive wildfires such as the Camp Fire in 2018 which destroyed Paradise (CA).
New York State alone has 16,000 miles of above ground utilities that it has evaluated putting underground as the costs and impacts of downed power lines has been climbing in recent years. NYS estimated it would cost $261B to bury all 84,480,000 feet (>$3K per foot) of so-called ‘dry utilities’. Ouch! Other undergrounding estimates range from $350 – $1,150 per foot. While this investment could save future costs of recovery and maintenance for utilities, it is unlikely that this level of investment will be prioritized for the vast majority of cables uglifying our landscapes and killing countless birds and mammals.
However, undergrounding could provide an unparalleled opportunity for rebalancing atmospheric carbon by displacing some portion of the sand used as backfill in the trenches with biochar. Sand is used as part of the backfill for a number of reasons; it serves as an insulator and a buffer to prevent damage to the conduit from rocks and it compacts well. Biochar could easily enhance the insulating properties and also serve as a buffer. Sized right biochar also compacts well.
A little back of the envelop math shows what a huge carbon sync this could be. Between 6: – 12” of sand is used under and above the conduits. Optimistically, 120 lbs of compacted sand is used per cubic foot. Let’s assume a fairly narrow 2’ wide trench is used so that for each 1’ in length, 240 lbs of sand is deployed. Displacing only 10% by weight with biochar would be 24 lbs of biochar per foot or 62 tons per narrow mile. [It’s likely that more than 10% could be used if the economics support it but civil engineers will need to test different ratios to understand what the optimal recipes might be in different soils and weather conditions.] There are roughly 5.5 million miles of cables on poles in the US, 2.2 million miles of water pipelines and 300,000 miles of natural gas pipelines. Imagine if regulators required the use of biochar in all new underground pipeline trenches including those being built for renewable natural gas, and new solar and wind farms.
Could this be a last ditch effort to bury carbon for good? I have spoken about this concept with some very large utility companies, especially those that are responsible for managing vast amounts of tree debris along power lines. So far though I don’t believe it has been commercially demonstrated. Who will be the first?
