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New proposal to treat city's waste takes aim at sewage

Original post made on Feb 11, 2014

Palo Alto may still be years away from building a state-of-the-art facility to process local food waste and yard trimmings, but officials are preparing to pick up the pace when it comes to dealing with sewage sludge, the third stream in the city's complex waste flow.

Read the full story here Web Link posted Tuesday, February 11, 2014, 9:32 AM

Comments (18)

Posted by former resident, a resident of Fairmeadow
on Feb 11, 2014 at 10:59 am

Perhaps a City Owned and Operated facility for converting waste to energy would be best. UC Davis just recently completed a facility of this kind...after 10 years of research and preparation! I recommend contacting the university to learn more. No sense reinventing the wheel if they have already gone through the process with a successful result!
Former Fair Meadow Resident


Posted by Cedric de La Beaujardiere, a resident of Barron Park
on Feb 11, 2014 at 11:02 am

Cedric de La Beaujardiere is a registered user.

Gennady, small correction: the Measure E election was in 2011, not 2012.

Thank you for covering this issue, and sitting through oh-so-many Council meetings to keep us all informed.

Also, when you wrote "The final piece of the puzzle in staff's plans would be to find a new site for processing yard trimmings, according to a staff report." That's partly right but not complete. We have a site to handle it: the Measure E site. However, yard trimmings currently go to ZBest in Southern Gilroy for aerobic composting. Staff said they would continue to look for alternatives, such as San Jose's Dry AD which uses a small amount of woody material to bulk up the primary food scraps input (but San Jose has all the wood they need for now and can't take ours). Staff also will continue to monitor the maturation of technologies for converting plant materials to energy, such as pyrolisis (which can produce biochar, possibly useful for carbon sequestration). The measure E proponents will likely encourage staff to take a closer look at local composting as well. Personally, I think staff should consider the life-cycle differentials in both cost and green house gas emissions for local vs distant composting (and not loose sight of other benefits like a closer source of compost for residents).


Posted by Creighton Beryl, a resident of Barron Park
on Feb 11, 2014 at 12:46 pm

"technologies for converting plant materials to energy, such as pyrolisis (which can produce biochar, possibly useful for carbon sequestration)."

Pyrolysis is a very poor option for converting plant materials to energy. Upfront it applies energy to bake the water and some partially flammable gases out of the plant materials (which are composed mainly of lignin, a carbohydrate), leaving behind what is essentially charcoal (which is an unfancy term for biochar).

Evaporating the water is a huge energy sink, and it produces none in return. The energy yield from the gases is at best marginal after one accounts for the energy invested to produce them.

The real energy yield from pyrolysis comes from burning the carbon in the biochar to CO2, which unsequestrates the carbon and puts it right back into the atmosphere as a greenhouse gas. You cannot have it both ways.

Run the numbers and see for yourself. Here's a bunch of them: Web Link


Posted by Keeping an eye out, a resident of Duveneck/St. Francis
on Feb 11, 2014 at 2:25 pm

How many times do we have to repeat it before this reporter gets it right? Not all proponents of Measure E wanted to build any kind of facility. The measure was a vote to enable STUDY of the possibility, not necessarily a decision to build a factory. Consider -- the immense environmental, recreational, historical, and aesthetic value of having those acres returned to their original master planned use -- a park! This news outlet and reporter need to consider more perspectives...


Posted by Cedric de La Beaujardiere, a resident of Barron Park
on Feb 11, 2014 at 3:46 pm

Cedric de La Beaujardiere is a registered user.

@Creighton: I appreciate your thoughts and agree that generally we should avoid wasting energy evaporating water, which is the main reason I was dubious about using gasification for wet sewage sludge. However, keep in mind that all options for handling our green bins will require energy. Currently the energy goes into trucking the plant materials to southern gilroy, and all the machines involved in sorting out trash, grinding big pieces into smaller, creating windrows, turning them and keeping them at the right moisture, aeration, & temperature, and then sorting out the compost from the bits that need another go round. The least energy input might conceptually be to make a big pile and leave it alone, but then we'd get anaerobic conditions producing and releasing methane, a powerful GHG. Really the best is for people to compost at home, the energy input being their own brawn, but this does not address all cases, like dealing with weed seeds, ivy, or thick wood and where would we handle material from apartments, businesses, city trees and parks? So centralized management has its place. A life-cycle analysis of cost, energy, and GHG of the options will help us make an informed and sensible choice.


Posted by Creighton Beryl, a resident of Barron Park
on Feb 11, 2014 at 4:09 pm

I think all sides in this issue ought to step back, analyze their proposals, and represent them with scientific accuracy free of hype and wishful thinking.

Biochar is simply not a viable garbage to energy strategy if the objective is to prevent greenhouse gases. In fact, ALL garbage to energy options put the sequestered carbon back into the atmosphere, for a pitifully tiny energy return.

The plants have removed the CO2 from the air. We should not put it back.


Posted by Craig Laughton, a resident of College Terrace
on Feb 11, 2014 at 7:27 pm

>The plants have removed the CO2 from the air. We should not put it back.

That statement defies the laws of chemistry and physics. Please defend it.



Posted by musical, a resident of Palo Verde
on Feb 11, 2014 at 9:05 pm

Care to clarify which laws of chemistry or physics?


Posted by Craig Laughton, a resident of College Terrace
on Feb 11, 2014 at 9:15 pm

>Care to clarify which laws of chemistry or physics?

Fixed carbon in plants always returns to CO2, which rises into the atmosphere.


Posted by musical, a resident of Palo Verde
on Feb 11, 2014 at 11:07 pm

I guess coal doesn't know that law until we dig it up and burn it.


Posted by Creighton Beryl, a resident of Barron Park
on Feb 12, 2014 at 10:52 am

"That statement defies the laws of chemistry and physics. Please defend it."

Photosynthesis, Mr. Laughton, it's called photosynthesis. I first learned of it in my fifth grade science book, but that was a while ago and they probably teach it in the fourth or even third grade now. Give it a Google.


Posted by Craig Laughton, a resident of College Terrace
on Feb 12, 2014 at 1:37 pm

>Photosynthesis, Mr. Laughton, it's called photosynthesis

And then what happens when the plant dies, or is trimmed? Are you suggesting that it get buried into a peat bog (the beginning of the coal cycle), or some deep mineshaft? Or might you suppose that aerobic bacteria and fungi convert the fixed carbon into CO2? The anaerobic digestion promoters want to convert the carbon into methane, then combust the methane to CO2, in order to power generators (to make electricity). But then they are still left with processed human sewage sludge and/or plant compost that might be hard to get rid of.


Posted by Creighton Beryl, a resident of Barron Park
on Feb 12, 2014 at 3:31 pm

" or some deep mineshaft?"

That's actually the best idea I've seen. Sterilize it and stuff it.

You and I agree. The carbon inevitably gets dumped back into the atmosphere in the normal course of nature or by deliberate combustion. Biochar is one way to lock it up. Dump that in a mine shaft, seal off the oxygen, gone.

My point for the innocents promoting this boondoggle is that we cannot have carbon sequestration and significant net energy yield simultaneously. Unless, of course, they wish to add a complex, very costly CO2 sequestration process on the exhaust stack, as some coal-fired generators do. There's your basic super-expensive boutique electricity.


Posted by Craig Laughton, a resident of College Terrace
on Feb 12, 2014 at 9:20 pm

>My point for the innocents promoting this boondoggle is that we cannot have carbon sequestration and significant net energy yield simultaneously.

Agreed. That is a serious scientific argument.

The problem is that carbon sequestration is a fantasy...there are not enough deep mines to handle the issue. It is better to avoid multiple transportation issues, and just deal with the refuge issue directly, which means plasma arc gasification, or something similar, at the Palo Alto site...which means that our garbage and sludge will turn into CO2, with an electricity bonus. And with no serious residue burdens.


Posted by Cedric de La Beaujardiere, a resident of Barron Park
on Feb 13, 2014 at 2:05 pm

Cedric de La Beaujardiere is a registered user.

This article: Web Link describes a UK waste water treatment plant which analyzed energy balances of various options and settled on Thermal Hydrolysis (TH) followed by Anaerobic Digestion (AD) followed by Dewatering, Drying, and Energy Recovery (ER) (using an existing incinerator but could be done by gasification or pyrolisis). Theirs is a massive plant serving millions of people, whereas our Regional Water Quality Control Plant (RWQCP) serves on the order of 100,000-ish (PA + nearby cities).

I derive from this three points:
1) more net energy is produced through TH+AD+ER than through either ER alone or TH+AD alone;
2) TH+AD halved the required capacity of their ER equipment;
3) if RWQCP finds it has trouble selling the fertilizer produced by the proposed TH+AD, it could cap the process with Energy Recovery (using a non-combustion technique like gasification rather than incineration).


Posted by Craig Laughton, a resident of College Terrace
on Feb 14, 2014 at 4:28 pm

>3) if RWQCP finds it has trouble selling the fertilizer produced by the proposed TH+AD, it could cap the process with Energy Recovery (using a non-combustion technique like gasification rather than incineration).

Cedric, I have to admire your edging towards the truth: Plasma arc gasification is NOT combustion, until the syngas (molecular hydrogen and carbon monoxide) is combusted to generate electricity...when it turns into CO2, similar to other combustion schemes to produce electricity, including anaerobic digestion).

The study you cite is interesting, within the narrow confines of avoiding plasma arc. Dewatering is a big issue, in terms of net energy, but supplemental sources of high heat value sources, like used tires (another big environmental pollutant), can make up the difference...only plasma arc can do this, without creating a pollution mess.

At the end of the day, human sewage sludge will end up as CO2. Why not use the Occam's razor approach, and choose the simplest solution, one that will limit the amount of CO2 produced: Plasma arc?


Posted by Cedric de La Beaujardiere, a resident of Barron Park
on Feb 18, 2014 at 10:56 pm

Cedric de La Beaujardiere is a registered user.

I would have been interested to evaluate a project like plasma arc, gasification, pyrolysis, or biochar (I know, some of these are subsets of the others). Unfortunately, none of the proposals included them, even though the RFP was designed to accommodate them (i.e., by specifying private ownership to protect the city from the risk of less vetted technologies). Therefore, it seems risky for Palo Alto to go ahead with one of these newer technologies, when apparently private companies are not yet ready to use one of these techniques for our organics.


Posted by Craig Laughton, a resident of College Terrace
on Feb 19, 2014 at 9:59 am

>Unfortunately, none of the proposals included them, even though the RFP was designed to accommodate them

Cedric,

Since your group stated that it would oppose technologies, such as plasma arc, and your group currently has the political power to impose its will, why would any private sector vendor bother to apply? Plasma arc has been shot down in various cities in the USA, by the political forces, like yourself, who are zero waste fanatics. The irony is that plasma arc is probably as close as possible to zero waste, because it turns the organics into electricity, and the inorganics into usable slag; it also eliminates the toxics in the incoming stream. I do give you credit, though, for being one of the few greenies that actually looks at plasma arc for what it is, and not what it is not. For example, plasma arc is not incineration or combustion, as your group once insisted...that is a big step in the right direction, in terms of public/political education. Who knows, maybe your side will even come to admit that all human sewage sludge and yard trimmings and food waste will end up as CO2, and the reside will still contain most of the toxins in the incoming stream, and that residue could become a major liability for Palo Alto...I am not holding my breath, but truth usually wins out in the end.


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