Grape Street dog park

A tree falls in an urban forest. Then what? It is chipped, hauled and disappeared. In the best case, it becomes furniture, art, mulch. The worst: its lifetime of carbon capture goes up in smoke.

If it's a palm tree, Miramar Greenery won't even take it. In any case, the city's curbside recycling doesn't accept tree stumps longer than four feet, limbs longer than six feet, or any one piece over six inches in diameter.

"End-of-life urban wood in the San Diego region is mostly wasted," according to Lumbercycle, a nonprofit sawmill in National City that turns fallen trees into lumber and other items.

"The majority goes into landfills or is chipped and used as mulch or groundcover, which disintegrates fairly rapidly."

As the city begins to fold organic waste into its recycling ordinance, trees are hardly mentioned in the discussion of landscaping leftovers. But drought and disease are turning many of them into urban wood waste.

According to Calrecycle, which oversees the state's organics recycling laws, such waste is mostly made up of lumber, trim, pallets, branches, stumps, and whole trees from street and park maintenance.

California’s SB 1383 set a statewide target of 75 percent organic waste reduction from the 2014 level by 2025. In addition to food waste, organics include landscaping leftovers and nonhazardous wood waste.

In the landfill, decaying organics release methane, a super pollutant 84 times worse than carbon dioxide, into the atmosphere.

Currently, approximately 30 percent of the residential waste entering the Miramar Landfill is recyclable green material. (In 2005, the amount was 14 percent, according to city files.

Up-recycled palm

Besides palms, the city declines to take banana and coral trees in curbside recycling since they create poor-quality mulch and compost and may damage the grinding machinery.

For city-owned trees, San Diego contracts with West Coast Arborists, a municipal tree maintenance contractor, among others. The contract only states that the contractor is responsible for cleaning up the debris and hauling it away.

While West Coast Arborists have an urban wood program that recycles many trees into raw lumber, less healthy specimens are sold as firewood or sent to the landfill. "Firewood is traditionally the most common use of large branches and logs."

The carbon released when such wood is burnt isn't accounted for in the city’s greenhouse gas emissions calculations.

Kensington resident and tree advocate Maggie McCann thinks a greener strategy would be letting the firewood-grade wood decompose underground, "as that process takes 50-100 years to complete, so the carbon would be either stored underground, or released slowly over time into the atmosphere."

The fate of most downed trees, however, is in the hands of private waste haulers, since the city does not collect big items like trees.

Lumbercycle will sometimes pick up logs from homeowners to be donated to their program.

According to Lumbercycle, while there are over 40 uses for tree biomass, the four that make the most economic sense for the San Diego region are lumber for building; wood pieces for furniture and arts; biochar to save water and provide soil nutrients; and fuel pellets that produce energy for local use.

Most valuable is the trunk and large branches where most of the carbon is stored. Not all tree species are good candidates for the four product types - especially palms, due to their fibrous trunks and fronds, which points back to the beginning of the zero waste loop: "plant right."

Still, a post on their Facebook page shows even downed palms can be given new life.

"Tried something with a piece of palm I got from Lumbercycle. Turned out better than I expected."