US 5,506,123 AGranted

Municipal solid waste processing facility and commercial lactic acid production process

AssigneeControlled Environmental Systems Corporation

InventorsRodger Chieffalo, George R. Lightsey

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Abstract

A method of processing waste is disclosed wherein the municipal solid waste is segregated and processed to recover reusable rubber, metal, plastic, glass and the remaining organic portion of the waste stream is used to make lactic acid and other chemicals. One process utilizes a pretreatment step with dilute sulfuric acid to reduce the heavy metal content of the cellulosic component of the municipal solid waste which may contaminate the produced lactic acid or inhibit the fermentation of the sugars obtained from such waste. In another, the heavy metal content of the cellulosic component of municipal solid waste is removed via an ionic exchange process, after hydrolysis with sulfuric acid. A process for an economical, energy efficient production of lactic acid from municipal solid waste is also disclosed.

Claims22

Dependent claims

A method for producing lactic acid from municipal solid waste, comprising the following steps:

(a) obtaining municipal solid waste;
(b) removing tires, bulk ferrous and non-ferrous metals, plastic, glass and rubber from the waste to give a cellulosic component;
(c) shredding the cellulosic component obtained in step (b);
(d) treating the shredded cellulosic component with dilute sulfuric acid at a temperature of 40.degree. to 100.degree. C. to solubilize substantially the remaining heavy metals and give a soluble component and an insoluble component;
(e) removing the soluble component obtained in step (d) from the insoluble component;
(f) drying the insoluble component obtained in step (e);
(g) treating the dried insoluble component obtained in step (f) with about 1:1 concentrated sulfuric acid to insoluble component, by weight, to give a partially hydrolyzed mixture;
(h) diluting the partially hydrolyzed mixture obtained in step (g) with water at a temperature of about 80.degree. to 100.degree. C.;
(i) agitating the diluted mixture obtained in step (h) at about 100.degree. C. to give a digested material;
(j) removing the solids from the digested mixture obtained in step (i) to give a filtrate;
(k) separating the filtrate into an acid containing solution and a sugar containing solution;
(l) concentrating the sugar containing solution to about 1-20% sugar;
(m) adjusting the pH of the concentrated sugar containing solution obtained in step (l) to about 4.5 to 7.5;
(n) fermenting the solution obtained in step (m) with lactic acid bacteria to give a solution containing lactic acid;
and
(o) processing the solution obtained in step (n) to obtain a commercially acceptable form of lactic acid.

13 more elements

A method for producing lactic acid from municipal solid waste, comprising the following steps:

(a) obtaining municipal solid waste;
(b) removing tires, bulk ferrous and non ferrous metals, plastic, rubber and glass from the waste to give a cellulosic component;
(c) shredding the cellulosic component obtained in step (b);
(d) treating the shredded cellulosic component with 1 to 10% sulfuric acid for 0.25 to 4 hours at a temperature of about 40.degree. to 100.degree. C. to solubilize substantially the remaining heavy metals and give a soluble component and an insoluble component;
(e) removing the soluble component obtained in step (d) from the insoluble component with a screw press;
(f) drying the insoluble component obtained in step (e);
(g) treating the dried insoluble component obtained in step (f) with about 1:1 concentrated sulfuric acid to insoluble component for about 10 minutes at about 30.degree. to 80.degree. C. to give a partially hydrolyzed mixture;
(h) diluting the partially hydrolyzed mixture obtained in step (g) with water at a temperature of about 80.degree. to 100.degree. C. to give a solution containing about 4 to 6 parts water to about 1 parts partially hydrolyzed material, by weight;
(i) agitating the diluted mixture obtained in step (h) for about 1 to 4 hours at about 100.degree. C. to give a digested material;
(j) filtering the digested mixture obtained in step (i) with a filter press to give a filtrate;
(k) separating the filtrate into an acid containing solution and a sugar containing solution by continuous ion exclusion chromatography;
(l) concentrating the sugar containing solution to about 1-20% sugar with a reverse osmosis filter;
(m) adjusting the pH of the concentrated sugar containing solution obtained in step (l) to about 4.5 to 7.5 with ammonia;
(n) fermenting the solution obtained in step (m) with lactic acid bacteria at about 25.degree. to about 40.degree. C. to give a solution containing lactic acid;
(o) filtering the lactic acid bacteria from the solution obtained in step (n);
and
(p) processing the filtered solution obtained in step (o) to obtain a commercially acceptable form of lactic acid.

14 more elements

A method for producing lactic acid from municipal solid waste, comprising the following steps:

(a) obtaining municipal solid waste;
(b) removing tires, bulk ferrous and non-ferrous metals, plastic, glass and rubber from the waste to give a cellulosic component;
(c) shredding the cellulosic component obtained in step (b);
(d) treating the shredded cellulosic component obtained in step (c) with about 1:1 concentrated sulfuric acid to solid component, by weight, to give a partially hydrolyzed mixture;
(e) diluting the partially hydrolyzed mixture obtained in step (d) with water at a temperature of about 80.degree. to 100.degree. C.;
(f) agitating the diluted mixture obtained in step (e) at about 100.degree. C. to give a digested material;
(g) removing the solids and essentially all of the heavy metals from the digested mixture obtained in step (f) to give a filtrate;
(h) separating the filtrate into an acid containing solution and a sugar containing solution;
(i) concentrating the sugar containing solution to about 1-20% sugar;
(j) adjusting the pH of the concentrated sugar containing solution obtained in step (i) to about 4.5 to 7.5;
(k) fermenting the solution obtained in step (j) with lactic acid bacteria to give a solution containing lactic acid;
and
(l) processing the solution obtained in step (k) to obtain a commercially acceptable form of lactic acid.

10 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/422,529Filed 14 Apr 1995 · continuation in part
Priority: 7 Dec 1994
Granted: 9 Apr 1996
Term ends: Not estimatedThe source records don’t support an estimate.

Classification11 codes

B03B 9/06
General arrangement of separating plant, e.g. flow sheets: specially adapted for refuse
C12P 7/56
Containing a carboxyl group including Peroxycarboxylic acids: lactic acid
Y02W 30/62
Reuse, recycling or recovery technologies: plastics recycling; Rubber recycling
Y10S 435/853
Using bacteria or actinomycetales: lactobacillus