SAPS: Getting more from orchard waste; cleaner air included

Number 3 in the Sustainable Agricultural Practices Series.

It is near impossible for all people to always agree on all matters, obviously. Take, for instance, climate change (global warming): 1) not everyone subscribes to the notion of a warming Earth; and 2) of those who believe the world is warming there isn’t universal consensus as to why this is. Some feel humans are behind it, while others disagree attributing such to natural forces. On this I think it is a fair assessment to say we’ll just have to agree to disagree and leave it at that.

One attribute, characteristic, element, phenomenon, call it what you will, people come together on is the notion of polluted air – that’s a given; it’s undeniable.

Where differences exist, these mainly center on what kind of and/or how much pollution is actually detrimental to the environment and human, animal and plant health. Sometimes conversation surrounding such can get very heated – and in a hurry. Many people seem to not burden themselves too much with matters of polluted air until they are directly affected by it. The reality is that there is more to contaminated, dirty, toxic, bad, hazardous, unhealthful, polluted – what-have-you – air than just meets the eye … and nose. Way more!

For years, in California, growers were given license to burn agricultural waste out in the open field sans any impunity. Today, it is an entirely different matter.

320px-BurningOffFieldsInTheEveningInSouthGeorgia[1]In the May 2003 Nut Grower magazine cover story: “Up In Smoke: If you’ve got money to burn, keep burning your orchard waste,” I opened thus: “The burning question of how to dispose of agricultural waste has some people scrambling for answers, particularly since waste from ag sources in the United States is considerable. It’s estimated that if just 30 percent of that waste were to be actually burned it would have a significant environmental impact. Incinerating refuse of any kind – farm-related or otherwise – releases harmful pollutants into the air we breathe and, due to air quality considerations in the San Joaquin Valley of California, any waste burning is only allowed on specific ‘permissive burn days.’”

I went on in the feature to list as well as describe ways growers can dispose of orchard waste without having to resort to burning it.

These were:

  • Chipping and shredding
  • Biomass (sometimes referred to as co-generation)
  • Cattle feed and animal bedding
  • GAC or granular activated carbon1

Each is described in significantly more detail below.

Wood chips

This one’s easy. Chipping and shredding, though it may cost more (the main costs come in the way of capital to either purchase or rent the chipping/shredding machinery – or one could hire a contractor to do the work) compared to pushing orchard brush out or toppling dead and/or decaying orchard trees into piles and hence burning (the per-acre costs to burn versus chipping or shredding was about $7 and $10, respectively, as determined by then Stanislaus County University of California Cooperative Extension Farm Advisor Roger Duncan and retired Merced County Farm Advisor Lonnie Hendricks through associated studies). With this alternative-to-burning method now at growers’ disposals, other uses for this ground-up material were found; either as a feed supply (or feedstocks) for biomass incineration (more on this in a moment) or as compost/soil-amending matter that could be reintroduced into planting/potting soils and that, according to Duncan and Hendricks via their research, “would produce a ‘long-term agronomic value,’” I reported. From the chipping/shredding processes, thus more environmentally friendly means of dealing with orchard waste on this order were identified.


Using orchard tree trimmings, prunings, etc. as a product for biomass or co-generation incineration, a byproduct of which can take any number of forms, unless there are on-site plants/facilities, this can be expensive to transport to such sites, one of the disadvantages of shipping said “biomass” – in some cases over long distances. Lately, there has been the problem of biomass burned in biomass plant- or co-generation-plant furnaces, from which electricity and heat are typically created, has lost its cost-competitive advantage compared to photovoltaic (solar cell) system and wind-farm installations, which has forced several biomass and/or co-generation sites in California to shut their doors recently. This has prompted some growers to come up with alternate solutions regarding orchard waste disposal. The methods which are coming to the fore have been very inventive, such as that which was covered yesterday in: “SAPS: Energy independence down on the farm.”

640px-California's_Central_ValleyBut, I will say that more than just electricity and heat is capable of being produced from biomass or co-generation furnaces. There is now the capability of converting much of the waste into liquid fuel that can be used, for instance, in trucks transporting said waste to biomass/co-generation sites, thereby creating what is called a closed-loop process thus bringing the entire process full circle, a process known otherwise as recycling. All of which, again, provides growers value while at the same time helps cut down on the amount of harmful pollution entering the air.

Animal feed/bedding

How apropos that I just finished eating my lunch consisting of a sandwich, the bread of which is made with raisins and chunks of walnuts. These are alternatively known as artisan or designer breads, breads which often contain a veritable cornucopia of ingredients, which I would imagine are all grown on the farm.

Focusing on one ingredient – walnuts – their shells like other forms of agricultural waste, too, must be disposed of. This task isn’t just limited to walnuts only. Think of all the kinds of nut varieties grown.

Well, there is good news. Real simply: as with chipping and shredding, nut shells (and hulls) can get ground up, reduced to fine bits and pieces.

When the “Up In Smoke” article was published in 2003, California was home to 1.4 million dairy cows. Each of those cows requires feeding. I also explained how the Golden State produced (at the time) a record 1 billion pounds of almonds the year prior. Also noted was that for every harvested pound of almonds (another huge California crop) produced was double that weight in hulls. In aggregate totals, 1 billion pounds of state-grown almonds yields 2 billion pounds of hulls.

Considering it takes three-and-a-half pounds of almond hulls to feed a cow daily, in 2002/2003 there was more than an ample supply of almond hulls to satiate California cows’ hungry appetites. In hard numbers, that’d be 1.825 billion (almond-hull) pounds. In other words, in this area there is plenty of room to spare.

But all hulls are not created equally. Some may be unfit for consumption by cattle/cows. In which case those of inferior quality could get mixed in with chipped and shredded wood, dirt, trash, well, you get the idea.

Relatedly, what can be done with almond and other nut shells? These can be ground up for animal bedding use. Presto! Problem solved.

Granular activated carbon

Granular-activated what?! Granular activated carbon or GAC, is what!

So check this out. “In 1993 Wayne Marshall, a research chemist at USDA’s Southern Regional Research Center began investigating a way to manufacture almond shells into … ‘GAC,’” I again wrote in “Up In Smoke.” Producing GAC from nutshells, the process is environmentally friendly, whereas GAC produced from coal, coconut shells, peat and wood is not. Interestingly, GAC has numerous uses, not the least of which is to filter or “efficiently absorb chemicals like acetonitrile, benzene and toluene from soils as well as to remove metals such as copper and lead from the air and water.” A follow-up report on what became of this then-experimental program seems justified.


  1. Alan Kandel, “Up In Smoke: If you’ve got money to burn, keep burning your orchard waste,” Nut Grower magazine, May 2003, pp. 6-7, 10

This post was last revised on May 21, 2020 @ 7:20 a.m. Pacific Daylight Time.

 – Alan Kandel

1 thought on “SAPS: Getting more from orchard waste; cleaner air included”

  1. It certainly makes more sense to burn wood waste as a fuel replacing fossil fuels than to simply burn in the open air. It would be beneficial if any wood that is burned be replaced with an equivalent new growth (CO2 absorption capacity) as that which is burned.

Comments are closed.