research article wastes to reduce emissions from

Research ArticleWastes to Reduce Emissions from Automotive Diesel Engines

Manuel Jimeacutenez Aguilar

Instituto de Investigacion y Formacion Agraria y Pesquera Consejerıa de Agricultura y Pesca Junta de AndalucıaCamino de Purchil sn PO Box 2027 18080 Granada Spain

Correspondence should be addressed to Manuel Jimenez Aguilar manueljimenezaguilarjuntadeandaluciaes

Received 2 September 2013 Revised 18 December 2013 Accepted 1 January 2014 Published 10 February 2014

Academic Editor Brajesh Dubey

Copyright copy 2014 Manuel Jimenez Aguilar This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The objective of the study was actually the investigation of the effect of various treatments on the ability of urine in absorbinggreenhouse gases Urine alone or mixed with olive-oil-mill waste waters (O) poultry litter (P) or sewage sludge (S) was used on theabsorption of CO

2and NO

119909from diesel exhaustThe absorption coefficient (098ndash029 g CO

2grNH

4) was similar to other solvents

such as ammonia and amines The ranges of CO2absorption(17ndash56) gl and NO reduction (09ndash37) gl in six hours indicate that

on average 20 litres of urine could be needed to capture CO2and NO

119909vehicle emissions from each covered kilometre The best

results of CO2absorption andNO

119909reduction were for urinemixed withO P and urine aloneThese wastes could be used to capture

CO2and NO

119909from automotive diesel engines to reduce gas emissionsThe proposed strategy requires further research to increase

CO2absorption and reduce the risks associated with waste-water reuse

1 Introduction

Diesel exhaust consists of a mixture of CO2 CO and

nitrogen oxides (NO NO2) In two agricultural tractors

using a portable exhaust-emission analyser Markisz et al[1] indicated emission values of CO

2of 40ndash80 gL NOx

of 04ndash1 gL and CO of 02ndash08 gL Carbon dioxide is themajor greenhouse gas in the world that needs to be reducedThere are various technologies used to separate CO

2from

flue gas These include chemical solvent methods physicalabsorptionmethods cryogenicmethodsmembrane systemsbiological fixation and the O

2CO2combustion process The

chemical solvent methods are generally recognized as themost effective technologies at present [2]

Nitrogen oxides (NOx) are considered to be a majorsource of air pollution and contribute greatly to photochem-ical smog acid rain ozone depletion and the greenhouseeffect NOx in diesel exhaust is usually composed of gt90NO

Reduction of nitric oxide flue gas emissions is prac-tised commercially both by the homogeneous process calledthermal NOx reduction and by heterogeneous processesunder the commonly used term ldquoselective catalytic reductionrdquo(SCR) Thermal reduction is usually operated around 900∘C

whereas SCR is typically operated at 350∘C [3] Commercialcatalysts are honeycomb monolith structures constituted byvanadia and tungsta the active components supported ontitania [4]

Selective catalytic reduction using urea as a reducingagent has been investigated for about 10 years and currentlyis a well-established technique to diminish NOx emissionsoriginating from heavy vehicles According to Koebel et al[5] themain reactions ofNOwith ammonia andurea produceN2 H2O and CO

2

4NH3+ 4NO +O

2997888rarr 4N

2+ 6H2O

2CO(NH2)2+ 4NO +O

2997888rarr 4N

2+ 4H2O + 2CO

2

(1)

A new mechanism of reaction has been proposed by Nova etal [4]

NO +NO2997888rarr N

2O3

N2O3+H2O + 2NH

3997888rarr 2NH

4NO2997888rarr 2N

2+ 4H2O(2)

NOx removal by urea over heterogeneous catalyst as well as inthe gas phase (homogeneous reaction) has been known to be

Hindawi Publishing CorporationJournal of Waste ManagementVolume 2014 Article ID 807947 5 pageshttpdxdoiorg1011552014807947

2 Journal of Waste Management

very effective to reduce the concentration of such a pollutantHowever the process requires slightly high temperature todecompose urea into NH

3and facilitate the surface reaction

over the catalyst [6]There is considerable practical interest in developing

a modified thermal reduction process that would operateefficiently at lower temperature

Several investigators refer to such reduction process asldquoselective non-catalytic reductionrdquo (SNR) SNR refers to NOxreduction by means of ammonia (or other reductants) in thepresence of mineral surfaces [3] So activated carbon wasproved to have high catalytic activity for SCR of NOx withNH3at low temperature The reduction of NOx in air was

attempted with urea supported on the activated carbon atroom temperature [6]

The mechanism for NOx reduction over mineral surfacesmay be similar to a mechanism that has been proposedfor V

2O5TiO2-SCR catalysts These main features are the

adsorption of NH3as NH

4on the surface adsorption and

oxidation of NO to NO2on the surface and formation and

desorption of the main reaction products N2and H

2O [3]

The main objective pursued in our current study isto establish a process for removal of CO

2and NOx at

room temperature without catalysts with relatively low-costand low-energy requirements For that we proposed thehydrolysed urine

The hydrolysis of urea is catalysed by the enzyme ureasean enzyme of which many microorganisms present in thewaste-water solution possess During the hydrolysis pH isincreased and NH

4is produced

CO(NH2)2+ 3H2O 997888rarr 2NH

4+HCO

3+OH (3)

NH4is in equilibrium with dissolved ammonia

NH4+OH 997888rarr NH

3+H2O (4)

The pKa value for this equilibrium is 93 at 25∘CAt the same time dissolved ammonia is in equilibrium

with gaseous ammonia Thus the decomposition of urea willlead to an increase of NH

4and pH and hence there will be a

risk of losses of nitrogen through ammonia evaporation [7]The ammonia from urine can be used to capture CO

2gas

and produce ammonium bicarbonate [8]

CO2(g) +NH

3(aq) +H

2O (l) 997888rarr NH

4HCO3(aq) (5)

If the aqueous ammonia is the agent that can simultaneouslyremove CO

2 SO2 and NOx plus HCl and HF that may exist

in the flue gas [9] it would possible to think that some organicwastes such as P [10] and S [11] like sources of ammonia(11 gKg 2 gKg resp) could be added urine and used tocapture CO

2and reduce NOx emissions from automotive

diesel enginesThe acidification is a method to inhibit decomposition

of urea and avoid ammonia losses [7] So addition of a lowpercentage of O (acid pH) could stabilize the CO

2absorbed

to reduce urine pH and thus ammonia volatilization [12]Human urine O and P are all materials that are produced

in large quantities as wastes of other processes and can be

obtained at reasonable prices Separating urine from waste-water at the source reduces the costs of extensive wastewater treatmentThe sanitation treatment of solid dry humanfaeces would be amuch easier process since it would bemoreaerobic and the amount of human faeces is low compared tothe amount of urine [13] Recovering the nutrients fromurineand other wastes and reusing them for agricultural purposesoffer the added benefits of resource savings [14]

The aim of the present work was to investigate the abilityof NH

4from O P and S to increase the CO

2-absorption

capacity of urine in automotive diesel engines Also the effectof bubbled wastes on the germination of tomato seed wastested

2 Materials and Methods

Five samples of hydrolysed urine were used at pH 9 8489 9 84 and electroconductivity (EC) 25 15 42 25 and15 dSmminus1 respectively The O collected from St Anthonyoil mill of Viznar (Granada Spain) in January 2011 had apH of 42 EC of 12 dSmminus1 PO

4-019 gL K-79 gL and total

polyphenols-31 gLFive samples (A B C D and E) of hydrolysed urine

were used as controlsThe different treatments were BP-urinemixed with 05 P in weight CS-urine mixed with 05 S inweight DO-urine mixed with 1 O in volume EPO-urinemixed with 2 O in volume and 1 P in weight All sampleswere stored in brown bottles with two replicates for eachtreatment Half samples (A1 BP1 CS1 DO1 and EPO1) werebubbled with fumes from the exhaust pipe of an agriculturaltractor (model 996E-Pasquali) For that each sample wasintroduced in a 25 litre plastic bottle A curved tube of forgeiron communicated the exhaust pipe with the bottom of thebottle To avoid heating the ignition engine was switchedonoff to intervals of 20 minutes So the bubbling time foreach sample was 6 hours (2 hours each day during 3 days)

In the end the pHof bubbled samples decreased to around80 All the samples were stored in 1-litre bottles open to air inthe laboratory for 5 months According to Hoglund et al [15]urine stored for at least 6 months may be considered safe touse as a fertilizer for any crop

Every two weeks the pH CO2 NH4 PO4 and K values

as well as the EC of each bottle were measured The pH wasmonitored using a pHionmeter and EC using a conductivitymeter (both Crison 2002) The CO

2was analysed following

the procedure reported by Lin and Chan [16] For thisafter determining the initial pH of the sample a 2mL urinesample was pipetted into a vial containing 10mL of 01 NHCl and the mixture was placed in a boiling water bathfor 10min to expel the CO

2 Allow the sample to cool to

room temperature add a magnetic stirrer and titrate with01 N NaOH Note the volume of NaOH added to achieve theinitial pH of the sample A blank containing 2mL of distilledwater was treated in an identical way The amount of CO

2in

mEqL was determined by multiplying the difference in thevolumes of NaOH required to titrate the blank and sampleby the normality of NaOH The NH


Nelson [17]The K+ was analysed by direct reading in a flame

Journal of Waste Management 3

Table 1 Main effects of diesel exhaust on the pH EC PO4 K CO2 and NH4 (average values for 14 measurements)

Treatment pH EC(dSm)

PO4(mgL)

K(gL)

CO2(gL)

NH4(gL)

CO2-Absorption(gL)

NH4 Reduction(gL)

Absorptioncoefficient

A 889b 279a 139a 17a 45a 52a

A1 836a 289b 164a 17a 85b 48a +406b minus042c 087cd

B 889b 221a 138a 13a 42a 40a

BP 881b 245b 135a 13a 55b 45b

BP1 817a 251b 144a 13a 82c 40a +263a minus047c 066bc

C 897b 422b 178a 33a 105a 85b

CS 894b 433c 196b 33a 108a 88b

CS1 837a 391a 196b 35a 122b 61a +167a minus275a 029a

DO 895b 390b 174a 30a 53a 76b

DO1 836a 368a 174a 31a 109b 59a +562c minus172b 098d

E 895c 267a 159b 14a 51a 53b

EPO 881b 295c 131a 18b 67b 56b

EPO1 822a 288b 152b 19b 84c 44a +175a minus125b 042ab

Different letters(a b c d) within a column indicate significant differences between treatments at level of significance (119875 lt 005) according to Tukeyrsquos test

photometer (model METEOR-NAK II) PO4analysis was

made by the method of Watanabe and Olsen in a UVVISspectrometer (model UNICAM 5625) [18]

21 Agricultural Test In this work the effects of bubbledwastes on the tomato-seed germination were tested Preciadoet al [19] studied tomato seedlings watered with four urinedilutions with different levels of EC The results showed astatistical significance in the growth parameters with thenutrient solution at the level of 1 dSmminus1

On the other hand according to Komilis et al [20] theO phytotoxicity decreased with increased O dilution withwater The higher the dilution the lower the phytotoxicityTo achieve a EC nearby to 1-2 dSmminus1 our bubbled sampleswere diluted to a ratio of 1 10 and 1 20 using tap waterThree seeds from tomato (Solanum lycopersicum) variety TresCantos were sown in each plastic cups measuring 7 cm times5 cm The plants were grown in a mixture of sand (20 g) andolive stone (5 g) On the first day 20mL of tap water wasuniformly added to each cup On alternate days 5mL ofbubbled wastes dilutions 110 or 120 or tap water (control)was added to each cup All samples including the controlwere run in duplicate The cups were kept in the laboratoryfor three weeks

The results were subjected to an analysis of varianceand comparison of means using the PC computer programStatistic 80 (Analytical Software FL USA) Also the figureswere plotted with this program

3 Results and Discussion

The average values of pH EC CO2 NH4 PO4 and K of each

treatment are shown in Table 1The treatments with diesel exhaust increased the CO

2

absorption in all samples indicating that part of CO2

(167ndash562 gL) was absorbed by the samples (Figure 1)

A A1 BP BP1 CS CS1 DO DO1 EPO EPO10

5

10

15

Treatment

CO2

(gL

)

Figure 1 Mean values of CO2

The treatment with the highest CO2absorptionwereDO1

(562 gL) and urine alone (406 gL) (see Table 1 Figure 1)Theoretically according to (5) absorption capacity of

ammonia was 25 (44 gCO217 gNH

3) Previous research

shows that aqueous ammonia have a higher absorptioncapacity than that of monoethanolamin (MEA) at the sametemperature and pressures Absorption capacity of aqueousammonia can be higher than 1 g CO

2g NH

3 and MEA is

only 036 gCO2g MEAThe CO

2removal efficiency with 1

aqueous ammonia was 50 in 1 hour [2] (in our researchmaybe similar)

Our research shows that the absorption capacity ofurine was similar to NH

3and MEA (between 098 and

029 gCO2gNH

4in 6 hours for treatment DO1 and CS1

resp)The higher CO

2absorption for DO1 samples could be

explained by the buffering capacity of O To more bufferingcapacity there are a smaller variation in pH for the additionof CO

2with a better stabilization of the CO

2absorbed [3]

Some treatment significantly reduced NH4contents (see

Table 1 Figure 2)The decrease in NH

4could be explained by assuming

as indicated by Wei et al [21] that NOx from flue gas can


0

2

4

6

8

10

A A1 BP BP1 CS CS1 DO DO1 EPO EPO1Treatment

NH

4(g

L)

Figure 2 Mean values of NH4

0 1 2 3

1

3

minus3

minus1

minus3 minus2 minus1

Stan

dard

ized

resid

uals

Figure 3 Correlation between pH CO2 NH4

react with NH3decomposed from ammonium bicarbonate

to produce N2

The treatments with the lowest NH4reduction were urine

alone (minus042 gL) and BP1 (minus047 gL) The greatest NH4

decrease in CS1 (minus275 gL) and DO1 (minus172 gL) samplescould be explained according to Buondonno et al [22] by thefact that some organic wastes can increase immobilization ofinorganic or mineralised N Moreover the fact that NH

4ion

linked with O in the presence of carbonates would reduceNH4in DO1 and EPO1 samples [12]

If we consider that NH4lost (04ndash17 gL) in our research

was due to NOx elimination then theoretically between07ndash3 gL of NO could be eliminated in 6 hours So our NOxremoval efficiencymay be similar 80NO removed in 20ndash40hours reported by Shirahama et al [6]

The dissolved exhaust fumes lowered the pH of the urinemixtures from90 to 83 due to the formation of carbonic acidThe lowering of the pH could be explained by the absorptionof CO

2on the one hand and the reduction of NH

4values on

the other handNH4volatilization increased with the pH so that all the

factors that tended to lower the pH reduced NH4losses [23]

Therefore all treatments to reduce the pH proved useful toNH4conservation

For all the samples the pH variations could be explainedin function of the CO

2and NH

4increases So the pH CO

2

and NH4showed a statistically significant relationship (119875 lt

00001) (correlation coefficient 0697) at the 95 confidencelevel (see Figure 3) NH

4contributed nearly 2-fold more than

CO2to the pH variation

pH = 841 + 015NH4minus 0 08CO

2 (6)

The increase in conductivity generated by CO2dissolu-

tion and ionisation in water was reduced by the decomposi-tion of urea and NH

4due to reactions with NOx [5]

In our laboratory CO2and NH

4contents of all samples

treated with diesel exhaust remained conservative for morethan five monthsThe better treatments (higher CO

2absorp-

tion with lower NH4reduction) were DO A and BP

Tables for different vehicles (gasoline diesel) indicateon average emissions values of 140 gCO

2and 2 gNOx for

kilometre With these values between 15 and 25 litres ofurine could be need to capture CO

2and NOx mean vehicle

emissions from each covered kilometre The urine producedby a family could be stored at home and be useful to reduceown vehicle emissions into towns

Nevertheless the advantages of this technology are unde-niable a process for removal of CO

2and NOx at room

temperature without catalysts with relatively low-cost andlow-energy requirements

Source separation of human urine is based on toiletsequipped with two bowls a front one for the collection ofurine and a rear one for faecal material Separating urinefrom faeces could have environmental advantages such asthe reduction of water consumption for human excrementdisposal (make savings 10ndash20 litres per person and day)Before the faeces collected separately could bemixed at homewith urban organic wastes to produced organic compost Soboth urine bubbled with greenhouse gases and faeces couldbe used as new fertilizers The atmospheric CO2 could beabsorbed in the urine solutions and added to alkaline soilscould be deposited as carbonate minerals

Some limitations Urine should be stored at home andcarried in the vehicle in a pressure container Before NH

4

contents in urine are variable and depend on diet and ambienttemperature which limits the CO

2absorption capacity (about

10 g by litre of urine)The urine and other wastes containing urea or ammo-

nium bicarbonate such as P by itself could be consideredsources of ammonia and useful to CO

2and NO absorption

31 Agricultural Test The results of the study showed thatdilution at the 1 20 level did not significantly diminish thegermination or growth of tomato plants for three weeksBecause the overall objective of the source-separation systemwas to use the wastes as a fertilizer it would be suitableto test these wastes for different crops over a completecrop cycle Fertilization with urine and O has previouslybeen demonstrated to be a feasible method for reducing theenvironmental impact of O nitrates and CO

2[24]

P and S could provide N and other plant nutrients whenused as fertilizers [25 26] Whereas part of added NH

4was

consumed to eliminateNOx the added sources ofNH4 (P andS) did not significantly increase CO

2adsorption Therefore

new wastes manures and compost need to be tested withadded urine as ameans for increasing NH

4contents and CO

2

adsorptionThus urine mixed with the above-mentioned wastes

could provide all plant nutrients and be recycled by thefertilizer industry


4 Conclusions

In conclusion hydrolysed urine mixed with a small percent-age (1-2) of O or P could be considered a stable long-term system for greenhouse-gas absorption An average of15ndash25 litres of these urine mixtures could be needed tocapture CO

2and NOx mean vehicle emissions from each

covered kilometre So the vehicle exhaust contaminationcould be reduced These wastes could be used as fertilizers

Some wastes similar to urine should be tested as CO2

sinks to produce new carbonated fertilizers In additionthe reduction of NOx emissions requires further research toincrease the NH

4contents and CO

2absorption

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This study was funded by the Institute of AgriculturalResearch and Training Andalusian GovernmentThe authoris grateful to the anonymous reviewers for insightful com-ments which greatlyfi improved the quality of the paper

References

[1] J Markisz P Lijewski and S Weymann The Measurement ofExhaust Emissions From the Engines Fitted in Agricultural Trac-tors Under Real Operating Conditions International Congressof Heavy Vehicles Road Trains and Urban Transport MinskRussia 2010

[2] J Liu S Wang B Zhao H Tong and C Chen ldquoAbsorptionof carbon dioxide in aqueous ammoniardquo in Proceedings ofthe 9th International Conference on Greenhouse Gas ControlTechnologies (GHGT rsquo9) pp 933ndash940 November 2008

[3] P H Wallman and R C J Carlsson ldquoNO119909reduction by

ammonia the effects of pressure andmineral surfacesrdquo Fuel vol72 no 2 pp 187ndash192 1993

[4] I Nova C Ciardelli E Tronconi D Chatterjee and B Bandl-Konrad ldquoNH

3-NONO

2chemistry over V-based catalysts and

its role in the mechanism of the Fast SCR reactionrdquo CatalysisToday vol 114 no 1 pp 3ndash12 2006

[5] M Koebel M Elsener and M Kleemann ldquoUrea-SCR apromising technique to reduceNO

119909emissions from automotive

diesel enginesrdquoCatalysis Today vol 59 no 3 pp 335ndash345 2000[6] N Shirahama I Mochida Y Korai et al ldquoReaction of NO with

urea supported on activated carbonsrdquo Applied Catalysis B vol57 no 4 pp 237ndash245 2005

[7] D Hellstrom E Johansson and K Grennberg ldquoStorage ofhuman urine acidification as a method to inhibit decomposi-tion of ureardquoEcological Engineering vol 12 no 3-4 pp 253ndash2691999

[8] M J Aguilar ldquoUrine as a CO2absorbentrdquo Journal of Hazardous

Materials vol 213-214 pp 502ndash504 2012[9] K P Resnik J T Yeh and H W Pennline ldquoAqua ammonia

process for simultaneous removal of CO2 SO2and NO

119909rdquo Inter-

national Journal of Environmental Technology andManagementvol 4 no 1-2 pp 89ndash104 2004

[10] D A R Diaz J E Sawyer and A PMallarino ldquoPoultrymanuresupply of potentially available nitrogen with soil incubationrdquoAgronomy Journal vol 100 no 5 pp 1310ndash1317 2008

[11] J Martin R M de Imperial E Beltran et al ldquoMineralizaciondel nitrogeno contenido en un lodo de depuradora secadotermicamenterdquo Revista Internacional Contaminacion Ambien-tal vol 22 pp 125ndash133 2006

[12] M J Aguilar ldquoFixation of ammonium-N and nitrate-N witholive oil mill wastewatersrdquo Environmental Technology vol 31no 4 pp 395ndash398 2010

[13] H Heinonen-Tanski A Sjoblom H Fabritius and P KarinenldquoPure human urine is a good fertiliser for cucumbersrdquo Biore-source Technology vol 98 no 1 pp 214ndash217 2007

[14] Z Liu Q Zhao K Wang D Lee W Qiu and J Wang ldquoUreahydrolysis and recovery of nitrogen and phosphorous as MAPfrom stale human urinerdquo Journal of Environmental Sciences vol20 no 8 pp 1018ndash1024 2008

[15] C Hoglund T A Stenstrom and N Ashbolt ldquoMicrobialrisk assessment of source-separated urine used in agriculturerdquoWaste Management and Research vol 20 no 2 pp 150ndash1612002

[16] S L Lin and J C M Chan ldquoUrinary bicarbonate a titrimetricmethod for determinationrdquo Clinical Biochemistry vol 6 no 3pp 207ndash210 1973

[17] D Nelson ldquoDetermination of ammonium in KCl extracts ofsoils by the salicylate methodrdquo Communications in Soil Scienceand Plant Analysis vol 148 pp 1051ndash1062 1983

[18] F S Watanabe and S R Olsen ldquoTest of an Ascorbic AcidMethod for determining phosphorus in water and NaHCO

3

extracts from soilrdquo Soil Science Society of America Journal vol29 pp 677ndash678 1965

[19] P Preciado A G Torres M A Segura et al ldquoEvaluation ofhuman urine as a source of nutrients in the production oftomato seedlingsrdquoUniversidad Y Ciencia vol 26 no 2 pp 171ndash178 2010

[20] D P Komilis E Karatzas and C P Halvadakis ldquoThe effect ofolive mill wastewater on seed germination after various pre-treatment techniquesrdquo Journal of Environmental Managementvol 74 no 4 pp 339ndash348 2005

[21] Z SWei Z Y Du Z H Lin HM He and R L Qiu ldquoRemovalof NO

119909bymicrowave reactor with ammonium bicarbonate and

Ga-A zeolites at low temperaturerdquo Energy vol 32 no 8 pp1455ndash1459 2007

[22] A Buondonno E Coppola G Palmieri et al ldquoMonitoringnitrogen forms in soilplant systems under different fertilizermanagements A preliminary investigationrdquo European Journalof Agronomy vol 7 no 4 pp 293ndash300 1997

[23] Z L He A K Alva D V Calvert and D J Banks ldquoAmmoniavolatilization from different fertilizer sources and effects oftemperature and soil pHrdquo Soil Science vol 164 no 10 pp 750ndash758 1999

[24] M J Aguilar ldquoOlive oil mill wastewater for soil nitrogen andcarbon conservationrdquo Journal of Environmental Managementvol 90 no 8 pp 2845ndash2848 2009

[25] D R Chadwick F John B F Pain B J Chambers and JWilliams ldquoPlant uptake of nitrogen from the organic nitrogenfraction of animal manures a laboratory experimentrdquo Journalof Agricultural Science vol 134 no 2 pp 159ndash168 2000

[26] T K Hartz J P Mitchell and C Giannini ldquoNitrogen andcarbon mineralization dynamics of manures and compostsrdquoHortScience vol 35 no 2 pp 209ndash212 2000

Submit your manuscripts athttpwwwhindawicom

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ClimatologyJournal of


very effective to reduce the concentration of such a pollutantHowever the process requires slightly high temperature todecompose urea into NH

3and facilitate the surface reaction

over the catalyst [6]There is considerable practical interest in developing

a modified thermal reduction process that would operateefficiently at lower temperature

Several investigators refer to such reduction process asldquoselective non-catalytic reductionrdquo (SNR) SNR refers to NOxreduction by means of ammonia (or other reductants) in thepresence of mineral surfaces [3] So activated carbon wasproved to have high catalytic activity for SCR of NOx withNH3at low temperature The reduction of NOx in air was

attempted with urea supported on the activated carbon atroom temperature [6]

The mechanism for NOx reduction over mineral surfacesmay be similar to a mechanism that has been proposedfor V

2O5TiO2-SCR catalysts These main features are the

adsorption of NH3as NH

4on the surface adsorption and

oxidation of NO to NO2on the surface and formation and

desorption of the main reaction products N2and H

2O [3]

The main objective pursued in our current study isto establish a process for removal of CO

2and NOx at

room temperature without catalysts with relatively low-costand low-energy requirements For that we proposed thehydrolysed urine

The hydrolysis of urea is catalysed by the enzyme ureasean enzyme of which many microorganisms present in thewaste-water solution possess During the hydrolysis pH isincreased and NH

4is produced

CO(NH2)2+ 3H2O 997888rarr 2NH

4+HCO

3+OH (3)

NH4is in equilibrium with dissolved ammonia

NH4+OH 997888rarr NH

3+H2O (4)

The pKa value for this equilibrium is 93 at 25∘CAt the same time dissolved ammonia is in equilibrium

with gaseous ammonia Thus the decomposition of urea willlead to an increase of NH

4and pH and hence there will be a

risk of losses of nitrogen through ammonia evaporation [7]The ammonia from urine can be used to capture CO

2gas

and produce ammonium bicarbonate [8]

CO2(g) +NH

3(aq) +H

2O (l) 997888rarr NH

4HCO3(aq) (5)

If the aqueous ammonia is the agent that can simultaneouslyremove CO

2 SO2 and NOx plus HCl and HF that may exist

in the flue gas [9] it would possible to think that some organicwastes such as P [10] and S [11] like sources of ammonia(11 gKg 2 gKg resp) could be added urine and used tocapture CO

2and reduce NOx emissions from automotive

diesel enginesThe acidification is a method to inhibit decomposition

of urea and avoid ammonia losses [7] So addition of a lowpercentage of O (acid pH) could stabilize the CO

2absorbed

to reduce urine pH and thus ammonia volatilization [12]Human urine O and P are all materials that are produced

in large quantities as wastes of other processes and can be

obtained at reasonable prices Separating urine from waste-water at the source reduces the costs of extensive wastewater treatmentThe sanitation treatment of solid dry humanfaeces would be amuch easier process since it would bemoreaerobic and the amount of human faeces is low compared tothe amount of urine [13] Recovering the nutrients fromurineand other wastes and reusing them for agricultural purposesoffer the added benefits of resource savings [14]

The aim of the present work was to investigate the abilityof NH

4from O P and S to increase the CO

2-absorption

capacity of urine in automotive diesel engines Also the effectof bubbled wastes on the germination of tomato seed wastested

2 Materials and Methods

Five samples of hydrolysed urine were used at pH 9 8489 9 84 and electroconductivity (EC) 25 15 42 25 and15 dSmminus1 respectively The O collected from St Anthonyoil mill of Viznar (Granada Spain) in January 2011 had apH of 42 EC of 12 dSmminus1 PO

4-019 gL K-79 gL and total

polyphenols-31 gLFive samples (A B C D and E) of hydrolysed urine

were used as controlsThe different treatments were BP-urinemixed with 05 P in weight CS-urine mixed with 05 S inweight DO-urine mixed with 1 O in volume EPO-urinemixed with 2 O in volume and 1 P in weight All sampleswere stored in brown bottles with two replicates for eachtreatment Half samples (A1 BP1 CS1 DO1 and EPO1) werebubbled with fumes from the exhaust pipe of an agriculturaltractor (model 996E-Pasquali) For that each sample wasintroduced in a 25 litre plastic bottle A curved tube of forgeiron communicated the exhaust pipe with the bottom of thebottle To avoid heating the ignition engine was switchedonoff to intervals of 20 minutes So the bubbling time foreach sample was 6 hours (2 hours each day during 3 days)

In the end the pHof bubbled samples decreased to around80 All the samples were stored in 1-litre bottles open to air inthe laboratory for 5 months According to Hoglund et al [15]urine stored for at least 6 months may be considered safe touse as a fertilizer for any crop

Every two weeks the pH CO2 NH4 PO4 and K values

as well as the EC of each bottle were measured The pH wasmonitored using a pHionmeter and EC using a conductivitymeter (both Crison 2002) The CO


the procedure reported by Lin and Chan [16] For thisafter determining the initial pH of the sample a 2mL urinesample was pipetted into a vial containing 10mL of 01 NHCl and the mixture was placed in a boiling water bathfor 10min to expel the CO

2 Allow the sample to cool to

room temperature add a magnetic stirrer and titrate with01 N NaOH Note the volume of NaOH added to achieve theinitial pH of the sample A blank containing 2mL of distilledwater was treated in an identical way The amount of CO

2in

mEqL was determined by multiplying the difference in thevolumes of NaOH required to titrate the blank and sampleby the normality of NaOH The NH


Nelson [17]The K+ was analysed by direct reading in a flame




PO4(mgL)

K(gL)

CO2(gL)

NH4(gL)

CO2-Absorption(gL)

NH4 Reduction(gL)


A 889b 279a 139a 17a 45a 52a


B 889b 221a 138a 13a 42a 40a

BP 881b 245b 135a 13a 55b 45b


C 897b 422b 178a 33a 105a 85b

CS 894b 433c 196b 33a 108a 88b


DO 895b 390b 174a 30a 53a 76b


E 895c 267a 159b 14a 51a 53b

EPO 881b 295c 131a 18b 67b 56b











2




5

10

15

Treatment

CO2

(gL

)







2g NH

3 and MEA is






029 gCO2gNH


resp)The higher CO




2absorbed [3]






0

2

4

6

8

10


NH

4(g

L)


0 1 2 3

1

3

minus3

minus1


Stan

dard

ized

resid

uals



to produce N2




4ion






4values on





2and NH


2





pH = 841 + 015NH4minus 0 08CO

2 (6)







2absorp-



2and 2 gNOx for





2and NOx at room




4





2and NO absorption


2[24]


4was




4contents and CO

2




4 Conclusions






4contents and CO

2absorption



Acknowledgments


References






3-NONO











119909rdquo Inter-











3
















Journal of












Volume 2014

Advances in









Geophysics

















PO4(mgL)

K(gL)

CO2(gL)

NH4(gL)

CO2-Absorption(gL)

NH4 Reduction(gL)


A 889b 279a 139a 17a 45a 52a


B 889b 221a 138a 13a 42a 40a

BP 881b 245b 135a 13a 55b 45b


C 897b 422b 178a 33a 105a 85b

CS 894b 433c 196b 33a 108a 88b


DO 895b 390b 174a 30a 53a 76b


E 895c 267a 159b 14a 51a 53b

EPO 881b 295c 131a 18b 67b 56b











2




5

10

15

Treatment

CO2

(gL

)







2g NH

3 and MEA is






029 gCO2gNH


resp)The higher CO




2absorbed [3]






0

2

4

6

8

10


NH

4(g

L)


0 1 2 3

1

3

minus3

minus1


Stan

dard

ized

resid

uals



to produce N2




4ion






4values on





2and NH


2





pH = 841 + 015NH4minus 0 08CO

2 (6)







2absorp-



2and 2 gNOx for





2and NOx at room




4





2and NO absorption


2[24]


4was




4contents and CO

2




4 Conclusions






4contents and CO

2absorption



Acknowledgments


References






3-NONO











119909rdquo Inter-











3
















Journal of












Volume 2014

Advances in









Geophysics















0

2

4

6

8

10


NH

4(g

L)


0 1 2 3

1

3

minus3

minus1


Stan

dard

ized

resid

uals



to produce N2




4ion






4values on





2and NH


2





pH = 841 + 015NH4minus 0 08CO

2 (6)







2absorp-



2and 2 gNOx for





2and NOx at room




4





2and NO absorption


2[24]


4was




4contents and CO

2




4 Conclusions






4contents and CO

2absorption



Acknowledgments


References






3-NONO











119909rdquo Inter-











3
















Journal of












Volume 2014

Advances in









Geophysics















4 Conclusions






4contents and CO

2absorption



Acknowledgments


References






3-NONO











119909rdquo Inter-











3
















Journal of












Volume 2014

Advances in









Geophysics


















Journal of












Volume 2014

Advances in









Geophysics














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