Stockpiles - The Issues

Wet weather degrades stockpiles of biomaterials (dewatered biosolids, composted materials, industrial organic wastes, manures, etc.).  They are liable to slump and/or to release run-off and/or odour.  This can be a water pollution risk, and a risk to property.  Whatever the site where the biomaterial is going to be used there will be a limited time window for application, but invariably the production facility is producing all the time.  Farmers etc. appreciate seeing the biomaterial on site (safely contained in an ARSC) so that they know that application is guaranteed.

Wet slumping stockpiles encroach on the surrounding land.  They are difficult to contain and, when the time comes to spread, application is slow, less precise, more difficult and more costly.  If you know your stockpiles might slump you should site them where the gradient is shallow; but this is a restriction on the land that can be treated and therefore increases costs.  

Can you contain a stockpile that starts to move?  It is difficult because the side pressures are immense.  Building a wall with large straw bales might be successful, but it is expensive in labour and materials and there is the problem of what to do with the rotting bales at the end of the job.   If rain continues, the stockpile can move the bales and then you need to secure them by driving stakes into the ground; that too can fail and release the contents.  If you push up earth walls you make a lagoon, with consequent risk of drowning, etc. unless you put up expensive fencing.

Will improving dewatering prevent slumping?  No - even digested biosolids that had been dewatered to 25%DS have slumped during wet winters.  

Lime stabilised dewatered biosolids do not slump.  That’s true but because stockpiles drain they lose leachate which is a water pollution risk.  An ARSC can also get over the pH>12 issue associated with this otherwise very useful treatment process.

Does compost need ARSC?  Yes it does; when stockpiles of composted materials become saturated with water oxygen is excluded; this sets up anaerobic conditions which produce compounds that are malodorous and/or phytotoxic.

Legal issues related to stockpiles.  In many countries it is an offence to make stockpiles that are not secure and contained.  In the EU there is added obligation if the pH is 12 or greater.  Odour nuisance can be a legal offence.  ARSC avoids all these issues.

What about adding structure and strength with bulking agent?  This can be done but it is more expensive than ARSC and it does not satisfy the legal obligation for safe containment.  Also there is the question of finding bulking agent free from contaminants (including weed seeds).