Comparing costs per gallon retained 

Soil amendment is one of the least expensive ways to collect and manage stormwater 

Manage water where it falls.” 

This sound advice is the foundation of the Milwaukee Metropolitan Sewerage District’s Regional Green Infrastructure Plana program that identified soil amendment as one of the least expensive ways to manage stormwater.  At 28 cents per gallon, improving soil is second only to native plantings in lowest cost per gallon retained. 

Green roofs?  $4.72 per gallon.  Those fancy-schmancy deep storage tunnels?  $2.42 per gallon.  At $1.59 per gallon, even pretty little rain gardens cost more than five times that of simple soil amendment. 

Milwaukee is not alone in promoting soil amendment as a first line of defense for stormwater management  For example: 

  • Denver and GreenleyColorado, require compost use for new landscaping, as does Leander, Texas. 
  • Some state Departments of Transportation (DOTs) now routinely specify compost.  A few years ago, the Texas DOT said it was the largest single market for compost in the U.S. 

In an urban environment, opportunities for soil amendment abound.  City parks, athletic fields, planters, urban lawns, highway medians and easements, foundation backfill – anywhere there’s soil, there’s opportunity for inexpensive water retention. 

Every 1 percent increase in soil organic matter (SOM) content adds an additional 16,000 gallons of water-holding capacity per acre foot.  A site managed to maintain soil organic matter at only 2 percent can hold all the water of a typical rain event (1 inch or less), which is 27,154 gallons per acre.     

In fact, at 5 percent SOM, the soil can retain the water equivalent of nearly 3-inches of rainfall.  In some regions, this equal95 percent of all storm events. 

Soil amendment may not solve all rainfall issues, especially in downtown areas.  But managing water where it falls can be the most sensible, efficient, environmentally- and economically-prudent strategy for “first line of defense” stormwater management.   

What if the world’s soil runs out?  Time/World explored this question in a “what if” interview about soil quality.

The subject? Seismic implications of soil erosion and degradation.  The focus? The quality of soil related to water conservation, food production, and other degradation impacts.

But a referenced study was even more thought-provoking.  It said between 1961 and 2003, 42% of observed sea-level rise could be linked to groundwater extraction.  Water from irrigation and other groundwater uses eventually flows to the rivers and streams.  These waterways feed the oceans.

Runoff is an indicator of depleted soil.

Rebuilding soil organic matter reduces water consumption,  stormwater runoff, and pollutant loads.  It cuts the use of agricultural chemicals, too.

Even issues not normally linked to compost use, like energy consumption, can improve.



Human activity and development destroy topsoil.  When topsoil goes, so does the soil’s natural ability to withstand the ravages of wind and water.  The result is erosion, and the by-product is sedimentation.
The wash and settling of soil particles reduces storage capacity of reservoirs.  Sediment clogs drainage ditches and navigation channels.  It buries fertile bottomland in sand.
This damage can make flooding worse. The cost of supplying drinking water and using water for generating electricity rises.
The USDA says sediment is “the greatest pollutant of waters in the U.S. by volume.”  Sedimentation is a costly thing to fix.  Mitigating the impact of sedimentation in the U.S. alone is in the billions of dollars.
Of course, humans aren’t responsible for all sediment loss.  Natural forces also erode stream banks and change shorelines.  But people do more than their share.
By one estimate, as much as two-thirds of sediment loss may result from the activities of people.
Compost use cuts sedimentation
Compost use reduces the impacts of farming, logging, development and other land disturbance.  It can also temper nature’s contribution to the problem.
Compost formulated for erosion control absorbs both rain energy and water.  When compost blankets are used, the amount of soil retained approaches 100 percent.  Water runoff is reduced by as much as 50 percent.
The place to focus sediment control is not on a river bed or estuary floor after the damage has already been done.  The best strategy is to manage sediment at the source — land disturbance activities.
Let compost play a central role in sediment prevention or soil restoration strategies.


why compostingA:  Composting saves natural resources, reduces landfill space requirements, protects the environment and saves money.

In addition, most fertilizers are manufactured from fossil fuels – not in abundant supply.  Distances from point of manufacture to markets are considerable, often over oceans.  Raw materials for compost manufacture are sourced locally.  Compost products are used locally.  Both reduce transport-related  energy consumption.

Why composting?  The #1 reason isn’t about recycling or diversion

It may surprise some that the #1 answer to “Why composting?” isn’t related to the process, but the product.  The most important reason to compost (the verb) is because it results in compost (the noun).

Finding ways to save landfill space and reduce the generation of greenhouse gases are important reasons to compost biodegradable materials.  But human activities deplete topsoil at an accelerated rate.  Compost is the only product that can economically, efficiently and naturally restore and maintain soil productivity.

Compost use builds organic matter.  A healthy soil requires less synthetic fertilizer.  It retains more rainwater, aids nutrient uptake, and degrades pollutants.

In fact, many of the problems related to water quality and water supply are related to poor soil quality.  The need to return organic matter to the soil through compost use cannot be under-valued as a tool for managing stormwater and improving water quality.