The new alchemy of hu­man waste

In 1812, the Broth­ers Grimm pub­lished Chil­dren’s and House­hold Tales, con­tain­ing many of the well-known and fa­mous fairy tales, such as Hansel and Gre­tel, The Frog Prince, and the fa­bled one of the long­haired Ra­pun­zel. One of those sto­ries was Rumpel­stilt

Cape Times - - INSIGHT -

First Ques­tion: Is there ac­tu­ally gold in toi­let waste?

Ac­cord­ing to Paul Wester­hoff and co-work­ers from Ari­zona State Univer­sity, there is ac­tu­ally gold and other pre­cious me­tal con­tained with hu­man sewage flushed down the toi­let.

In a study they con­ducted and pub­lished in the sci­en­tific pub­li­ca­tion En­vi­ron­men­tal Sci­ence & Tech­nol­ogy in 2015, they es­ti­mated that for a com­mu­nity of 1 mil­lion peo­ple, the me­tals con­tained in the sludge gen­er­ated from the waste­water treat­ment process had a value of around $13 mil­lion.

Fur­ther, a model they used to de­ter­mine the rel­a­tive po­ten­tial for eco­nomic value from the sludge showed that there are 13 lu­cra­tive ele­ments, in­clud­ing silver, cop­per and gold, with an es­ti­mated value around $280/ton of sludge.

While this sci­en­tific study showed that there are ac­tu­ally pre­cious me­tals con­tained in toi­let-de­rived waste, there is some way to go be­fore we re­ori­en­tate our en­gi­neer­ing pro­cesses to ex­tract these re­sources.

Mak­ing Gold from Fae­cal Waste: Chang­ing Our Mind­set: From Waste­water to Re­source Re­cov­ery Fa­cil­i­ties

In Au­gust, the au­thor at­tended the 2nd In­ter­na­tional Re­source Re­cov­ery Con­fer­ence held at Columbia Univer­sity, New York.

The three-day con­fer­ence aimed to show­case the lat­est de­vel­op­ments in re­source re­cov­ery from sew­er­age-de­rived and fae­cal sludge waste (Note: sew­er­age waste is that which is moved through sew­ers, and can be from do­mes­tic sources, in­clud­ing clothes wash­ing and toi­let use, and/ or in­dus­trial sources, for ex­am­ple, man­u­fac­tur­ing. Fae­cal sludge refers to waste that col­lects in on-site pit­type sys­tems, and in­cludes sep­tic tanks.)

The con­fer­ence was not only fo­cused on tech­nol­ogy, there was also a fo­cus on the mon­eti­sa­tion, fi­nanc­ing and pol­icy-mak­ing re­quired to drive re­source re­cov­ery in the form of en­ergy and com­mer­cially valu­able chem­i­cals. What was telling about the con­fer­ence was “waste” was not a word used to de­scribe their en­gi­neer­ing sys­tems – these sys­tems were called re­source re­cov­ery fa­cil­i­ties.

A New Ap­proach to Har­vest­ing Valu­able Com­modi­ties from Toi­let Waste

At­tend­ing the con­fer­ence was a young en­gi­neer, Dr Shash­wat Va­jpeyi, co-fun­der and chief ex­ec­u­tive of a biotech start-up named Car­bo­cy­cle, the tech­nol­ogy of which was de­vel­oped through his post­grad­u­ate re­search at the Chan­dran lab­o­ra­tory at Columbia Univer­sity and with fund­ing sup­port from the Bill & Melinda Gates Foun­da­tion.

In con­ven­tional waste­water treat­ment pro­cesses, sludge pro­duced from the waste­water treat­ment process is of­ten treated anaer­o­bi­cally – mean­ing in the ab­sence of oxy­gen – through spe­cialised mi­cro-or­gan­isms which thrive when there is no oxy­gen.

Through a cas­cade of re­ac­tions in­volv­ing a host of mi­cro-or­gan­isms, meth­ane gas is ul­ti­mately pro­duced.

The meth­ane pro­duced from the anaer­o­bic process can then be used for heat­ing or could be con­verted into elec­tri­cal en­ergy.

What Shash­wat and his team have shown is that they do not have to con­vert all the car­bon source in the waste to meth­ane – they ac­tu­ally en­gi­neer their sys­tems to pro­duce or­ganic acids, and in­stead of tak­ing this and fur­ther de­grad­ing ul­ti­mately into meth­ane, they feed it to oil-pro­duc­ing yeasts.

The oils pro­duced are sim­i­lar in com­po­si­tion to com­mon veg­etable oils, in­clud­ing palm oil, which are used in many man­u­fac­tur­ing pro­cesses, in­clud­ing cos­met­ics and soaps.

This process is not con­fined only to waste­water pro­cesses, but to other so-called “waste in­dus­tries” that have a lot of or­gan­ics con­tained within them.

In so do­ing, Shash­wat and his team aim to estab­lish a new in­dus­try based on con­vert­ing read­ily-avail­able or­ganic “wastes” into us­able chem­i­cals, thereby cre­at­ing new ma­te­rial sup­ply chains within ci­ties. To see more of the patented sys­tem, see this video:­jHatVZg8

In Ghana, the Columbia Univer­sity team led by Pro­fes­sor Kar­tik Chan­dran part­nered with a lo­cal univer­sity, Kwame Nkrumah Univer­sity of Sci­ence and Tech­nol­ogy, to adapt the process to make biodiesel from toi­let waste.

A pi­lot plant, guided by Columbia Univer­sity lab­o­ra­tory re­search, was es­tab­lished in Ku­masi and was fed with pit la­trine waste. Like the rest of sub-Sa­ha­ran Africa, full-sew­ered sys­tems are not com­mon in Ghana. In­stead, pit toi­lets are used – these tech­nolo­gies usu­ally rely on a hole in ground in which the fae­cal-ori­gin waste col­lects and even­tu­ally needs to be emp­tied.

This can be a costly process to the house­hold and for ser­vice providers who empty these toi­lets as part of their busi­ness, as prof­its are linked to af­ford­abil­ity of their ser­vice to con­sumers and the cost of dis­pos­ing the waste in an en­vi­ron­men­tally safe man­ner. A com­mon chal­lenge in the de­vel­op­ing world is that this waste of­ten ends up be­ing dis­posed into the en­vi­ron­ment.

What Pro­fes­sor Chan­dran’s team aimed to do was to show that through in­no­va­tive eng in­eer­ing pro­cesses, toi­let waste can be con­verted into valu­able prod­ucts with the fur­ther prom­ise of off-set­ting costs into the san­i­ta­tion sup­ply chain.

This has the po­ten­tial to re­duce the cost of ser­vices to cus­tomers re­quir­ing emp­ty­ing ser­vices and in­cen­tivis­ing pit-emp­ty­ing busi­nesses to bring the col­lected waste to these re­source re­cov­ery fa­cil­i­ties.

Sim­i­lar strate­gies are be­ing ex­plored else­where around the world (see: http://piv­ot­ pivot-fuel).

In South Africa, a novel treat­ment sys­tem for the treat­ment of the sludges col­lected from dry toi­lets was re­cently com­mis­sioned in Dur­ban.

The sludge pro­cess­ing plant, lo­cated south of Dur­ban, was built through a grant awarded to Khany­isa Projects by the Bill & Melinda Gates Foun­da­tion and us­ing a novel black soldier fly lar­vae tech­nol­ogy de­vel­oped by Agripro­tein and man­aged through its busi­ness off­shoot Bio­cy­cle, which is based near Cape Town.

The black soldier fly tech­nol­ogy

is an in­dus­trial bi­ol­ogy tech­nol­ogy in which Black Solider Flies, which have lim­ited life­span of up to eight days, lay eggs which de­velop into lar­vae.

The lar­vae eat waste prod­ucts – this was mostly con­fined to food wastes but has now been ap­plied to hu­man fae­cal waste – to re­duce its vol­ume.

These lar­vae gain sig­nif­i­cant weight in a few days and the flies, un­like house­hold flies, are not considered a pest, nor do they spread dis­eases.

These lar­vae can be fur­ther pro­cessed into pro­tein feeds and oils. In Dur­ban, the har­vested lar­vae are be­ing col­lected af­ter com­post­ing with a com­bi­na­tion of food and fae­cal-ori­gin waste for fur­ther pro­cess­ing into a branded prod­uct called “MagOil” (http://agripro­tein. com/our-prod­ucts/) (Fig.1).

The pi­lot aims to demon­strate cir­cu­lar econ­omy prin­ci­ples where prod­ucts are reused and re­cy­cled while pro­vid­ing san­i­ta­tion ser­vices, and is a plat­form to show­case the tech­nol­ogy to po­ten­tial part­ners who may be in­ter­ested in new sup­ply chains for their prod­ucts.

DR SUD­HIR PILLAY, re­search man­ager for San­i­ta­tion at the Wa­ter Re­search Com­mis­sion in Pre­to­ria, ex­plains the link.

BLACK GOLD: At the black solider fly lar­vae plant in Dur­ban, Sun Kim from the Bill & Melinda Gates Foun­da­tion takes a closer look at sludge pro­duced from har­vested lar­vae and, be­low right, oil pro­duced from har­vested lar­vae.

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