Water – There’s not a lot

When we think of the polar caps, Greenland, mountain glaciers, the Great Lakes, Lake Baikal, Lake Victoria, the great rivers, and all the aquifers around the world, it seems that there is lots of fresh water on earth, albeit much not accessible to us.  The picture shown by biomimicry scientist Janine Benyus at a TED Talk illustrates how little there actually is, including in the oceans.  I guess we think of the biosphere, the layer of water and air that supports all living things on earth, as like an orange rind, when in fact, it is more like an apple skin.

Besides our concerns over having enough clean, fresh water for people to drink, cook and wash with, industry and agriculture need water as well.   It is often stated that water is needed for energy, and increasingly, energy is needed for water (pumping over greater distances, desalination, effluent treatment discharge or re-use, etc.).  We address here particular issues of water needs for agriculture, and some potential solutions.  As Climate Change creates drought conditions in many places that previously had adequate rainfall and/or water for irrigation of crops, and as depletion of aquifers after decades of intensive withdrawal, agriculture needs to work hard to adapt.

Some of the most problematic venues include parts of California – Imperial Valley, Sacramento Delta, Central Valley, and coastal areas, where drought and aquifer depletions have created serious disruptions – Australia, where wheat and other crops have been at risk for over a decade due to droughts and extreme summer heat, much of Europe, India, South Africa, the West Coast of South America, where crops for export have been increasing production for a decade using irrigation from the Andes snow pack runoff, and other many places that are constantly in the news.

Many solutions involve modifying how agriculture is conducted, such as contour plowing, increasing no-till planting, cropping systems that reduce water runoff, seasonal cover crops, GPS-enabled targeted irrigation, and drip irrigation.  On a wider landscape level, water management with such as reservoirs and conservation set-asides of wetlands are important measures. 

Technological solutions include mulching, primarily with black plastic film mulch, which not only aids soil water retention, but also suppresses weeds and animal pests, thus mitigating use of crop protection chemicals. Therefore, it is highly favored by organic farmers.  However, there is great irony in that these farmers have typically rejected using film made of the highly biodegradable bioplastic PHA because it is produced by fermenting sugars with GMO microbes, despite the fact that there is no GMO material residual in the PHA, and none escapes the manufacturing system. They would rather use non-biodegradable petrochemical polyethylene film that needs to be removed and landfilled at the end of the season.  We need to get our heads straight about GMOs if we are going to feed 7 billion people or more.

Other options include soil amendments and additives that help soils to retain water and often provide other benefits, such as NPK and micro-nutrient retention, and harboring beneficial species of the soil microbiome.   These materials range from the natural, such as manure, humic acid amendments, and compost, to the manufactured, such as super absorbent polymers (SAPs), hydrogels, and bio-char.  The latter is being explored for its efficacy with various crops around the world, in the US, Australia, Europe, and Africa, and is emerging as a byproduct of a number of processes for thermochemical conversion of biomass to make fuels or chemicals, including Origin Materials, Proton Power, and Avello Bioenergy.   But biochar, also known as terra preta, has a centuries-long history, including at sites in the Amazon left by indigenous tribes practicing slash and burn agriculture on otherwise poor soils.  Similar sites exist in Ecuador, Peru, Benin and Liberia in West Africa.  So, for biochar, it looks like back to the future.

Author:

Ron Cascone, Principal