Evaluation of Food Waste and Paper-Cardboard Waste Blend for Biohydrogen and Methane Production Using Mixed Microbial Consortia

Evaluation of food waste and paper-cardboard waste blend for biohydrogen and methane production using mixed microbial consortia

Brahmaiah Pendyala¹, Subba Rao Chaganti², Jerald A. Lalman^3* Daniel D Heath⁴

¹Department of Civil and Environmental Engineering, Essex Hall, University of Windsor, 401 Sunset Ave., Windsor, ON, Canada, N9B 3P4. Email: pendyala@uwindsor.ca

²Great Lakes Institute for Environmental Research, University of Windsor, 401 Sunset Ave., Windsor, ON, N9B 3P4   Email: chaganti@uwindsor.ca

³*Department of Civil and Environmental Engineering, Essex Hall, University of Windsor, 401 Sunset Ave., Windsor, ON, Canada, N9B 3P4. (Corresponding Author): +1 519 253 3000 (ext.2519), +1 519 971 3686 (fax), Email: lalman@uwindsor.ca

⁴Great Lakes Institute for Environmental Research, University of Windsor, 401 Sunset Ave., Windsor, ON, N9B 3P4   Email: dheath@uwindsor.ca

 

Abstract

         A food waste and paper-cardboard waste blend was used to evaluate the H₂ production using a mixed microbial community.  At a feed concentration of 10 g COD/L, the maximum H₂ production (34±1 mL/g COD) was observed for linoleic acid (LA) treated cultures.  The microbial diversity data showed that Methanosarcina sp. was dominant in the 5 g/L COD untreated culture.   In comparison, methanogens were inhibited and the dominant populations were Lactobacillus sp. and Clostridium sp in the LA treated cultures fed with 10 g/L COD of the blended filtrate (food plus paper cardboard waste).  For the LA treated cultures fed with 5 g/L COD and 10 g/L COD, the H₂ yield were statistically the same.

 

Introduction

     Urban waste management is a key global concern because of environmental concerns such as local pollution issues and green house gas emissions.  According to 2010 data from the United States Environmental Protection Agency (USEPA), the estimated annual production of municipal solid waste (MSW) in the United States (U.S.) was 250 million tonnes with approximately 136 million tonnes (54.2 %) sent to landfills.  Conventional landfilling practices are unsustainable because it leads to the production of leachate and uncontrolled greenhouse gas emissions.  The organic fraction of MSW (OFMSW) in landfills is a large renewable energy asset.  OMSW can be converted into renewable fuels such as hydrogen and ethanol using bioprocessing technologies.  Developing bioprocesses to produce fuels and chemicals from OMSW will reduce the environmental pollution impact and add-value to a waste product.   Optimizing conditions to extract free sugars and minimize the formation of microbial inhibitory byproducts from treating OMSW using different technologies is challenging.  In the proposed work, steam explosion is used to extract free sugars from a synthetic OMSW and paper cardboard waste.

Materials and Experimental Methods

     Degrading a food waste plus a paper-cardboard blend by mixed anaerobic communities into H₂ and methane was assessed at 37șC, at a pH set at 5.5 and different organic concentrations.  The characteristics of municipal food waste from collection facilities are variable; hence, a synthetic food waste was prepared to minimize compositional variation. The waste was prepared based on unused portions of food pieces which consisted of protein, carbohydrates, vegetables and fats. The diet composition was in accordance with the Canada Food Guide (CFG, 2007) and thus, it was representative of Canadian kitchen waste.  The paper and cardboard slurry samples were prepared using 50 g paper and 50 g corrugated cardboard in 1.5 L water.  The solid waste samples were liquefied using a domestic food blender and water was added to prepare a slurry. The slurries were divided into three portions of which two were heated in a steam explosion reactor in batch mode with a working volume of 1 L. The two portions were heated separately for 1 h at 160șC, 180șC and the third portion not heat treated.

Results and Discussion

     The filtrate from heat treated and untreated samples were analysed for COD, free reducing sugars and furfurals (Table 1).  When compared to untreated samples, the COD concentration, the free reducing sugars and furfurals levels increased in the steam exploded samples. With increasing temperature conditions, the COD decreased and the free reducing sugar concentration reduced; however, the furfural (furfural and hydroxyl methyl furfural) quantities increased in the food waste steam exploded filtrate samples.  In contrast, the paper-cardboard waste filtrate samples showed an increase in the COD and furfural concentration and a slight decrease in the free reducing sugar concentration.

Table 1. Analysis of treated and untreated food and paper-cardboard waste samples

Sample	COD (mg/L)	Free reducing sugar (mg/L)	Furfural (mg/L)	Hydroxy methyl furfural (mg/L)
FW180 șC	98,800	17,357	469	6,100
FW160 șC	120,000	29,696	75.4	1,043
PW180 șC	5,207	2,584	44.8	50
PW160 șC	4,460	2,617	4.5	42.7
UTFW	63,867	21,495	N.A.	N.A.
UTPW	1,787	958	N.A.	N.A.

Notes: FW180șC = food waste treated at 180șC; FW160șC = food waste treated at 160șC; PW180șC = paper-cardboard waste treated at180șC; PW160șC = paper-cardboard waste treated at160șC; UTFW = untreated food waste; UTPW = untreated paper-cardboard waste  

  Because of inhibited microbial growth, decreasing H₂ production was detected in cultures not treated with LA but fed with the steam explosion samples treated at 180 ^oC and containing higher furfural concentrations.  According to Modig et al. (2002), furan derivatives are known to inhibit many metabolic pathways. The higher concentration of furan derivatives in the samples treated at 180șC can behave as inhibitors and decrease the H₂ yield.  The lower COD content of 4.46 g COD/L for the paper-cardboard waste treated at 160șC was unable to produce a maximum H₂ yield (Ginkel et al., 2001). To eliminate the inhibitory problem, a compromise option was developed by blending the food and paper-cardboard waste treated at 160șC to enhance the H₂ production potential.  This blend was used as a feedstock for the anaerobic cultures.

      Mixed microbial anaerobic cultures at an initial pH value of 5.5 and at 37 ^oC were treated with linoleic acid (LA) and without LA and fed with the filtrate blend to assess their H₂ producing capacity.  For the untreated cultures fed with 5 and 10 g COD/L of the blend, the H₂ yield reached 8.9±1 and 17±2 mL/g COD, respectively. In comparison, when the cultures were treated with LA and 5 and 10 g COD/L of the steam exploded samples, the H₂ production was

Fig 1. Biohydogen and methane production potential of both treated and untreated cultures

Notes: 5UT = 5 g COD untreated culture; 5T = 5 g COD treated culture (LA); 10UT = 10 g COD    untreated culture; 10T = 10 g COD treated culture (LA).

32±2 and 34±1 mL/g COD, respectively.  The data clearly revealed that compared to higher methane producing untreated cultures, the LA treated cultures significantly inhibited methane production by suppressing methanogenic growth and subsequently, increasing H₂ production (Ray et al., 2008; Chaganti et al., 2011; Saady et al., 2012). 

Conclusions

     The optimum COD concentration for higher H₂ production (34±1 mL/g COD) was observed at a feed concentration of 10 g COD/L.  Microbial diversity data showed that Methanosarcina sp., a methanogen, was the dominant microbial population in the 5 g/L COD untreated culture.   In comparison, in cultures fed with 10 g/L COD of the blended filtrate (food plus paper cardboard waste) and treated with LA, methanogens were inhibited and the dominant populations were Lactobacillus sp. and Clostridium sp.  The H₂ yield were statistically the same for the LA treated cultures fed with the two different COD concentrations (Figure 1).

REFERENCES

USEPA, 2010. Municipal Solid Waste Generation, Recycling and Disposal in the United States: Facts and Figs. for 2010. <http://www.epa.gov/msw/facts.htm>.

CFG, 2007. <www.hc-sc.gc.ca/fn-an/alt_formats/hpfb-dgpsa/pdf/food-guidealiment/ view_eatwell_vue_bienmang_e.pdf>.

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Saady N.M.C., Chaganti S.R., Lalman J.A., Heath D. (2012). Impact of culture source and linoleic acid (C18:2) on biohydrogen production from glucose under mesophilic conditions. Int J Hydrogen Energy. 37, 4036-4045.