Module 4.10Ecosan versus conventional

sanitation

How can dry UD ecosan system be compared with a conventional

systems (open defecation, latrine pit, water-borne)?

4 Swedish systems with nutrient recovery compared

1. Reference. Conventional system. N & P removal in WWTP. Effluent: 8 mg N & 0.24 mg P/l. Sludge incinerated, ash landfilled.

2. Urine. 80% of urine diverted & recycled as fertiliser. Rest = reference

3. Blackwater. Vacuum toilets. Collected blackwater anaerobically digested, sanitised & recycled as fertiliser. Rest = reference

4. Sludge. Sludge recycled as fertiliser. Rest = reference

Recycled plant available NPKS

0

10

20

30

40

50

60

70

80

Reference Urine Blackwater Sludge PhoStrip KREPRO BioCon

Rec

ycle

d pl

ant

avai

labl

e N

PK

S (

% o

f to

t) N P K S

Energy use

0

100

200

300

400

500

600

700

800

900

1000

Reference Urine Blackwater Sludge PhoStrip KREPRO BioCon

Ene

rgy

use

(MJ/

pers

, yr

)

Pumping Treatment Transports P-recovery Spreading Chemical fertiliser

Total use non-renewable

0

100

200

300

400

500

600

Reference Urine Blackwater Sludge

No

n-r

en

ew

ab

le r

eso

urc

e u

se (

10

e-1

6/p

ers

on

, yr

)

P,K,S Oil, gas Electricity

Other studies of sorting systems

• Many systems analysis have found same results:

• Urine diversion – decreases water emissions – gives lots of useful fertiliser– saves chemical fertiliser– saves energy

Recycled NPK vs degree of diversion

0,0

0,5

1,0

1,5

2,0

2,5

3,0

NConv

N40%

N100%

PConv

P40%

P100%

KConv

K.40%

K100%

Rec

ycle

d N

PK

[kg

/p,y

r] Urine

Sludge

Water emissions vs degree of diversion

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

N Conv N 40% N 65% N 100% P Conv P 40% P 65% P 100%

Wat

erem

issi

ons

[kg/

p,ye

ar] Sew plant

Field

Landfill

Chemicals

Energy usage vs degree of diversion

http://www.stockholmvatten.se/pdf_arkiv/english/Urinsep_eng.pdf

0

50

100

150

200

250

300

350

Conv 40% Urine 65% Urine 100% Urine

Ene

rgy

usag

e [M

J/p,

year

]

Fertiliser

Oil

Electric

Energy usage vs transport distance

0

50

100

150

200

250

300

350

400

Conv. 1 kmUrinetruck

33 kmUrinetruck

100 kmUrinetruck

200 kmUrinetruck

1 kmUrine

t+t

33 kmUrine

t+t

100 kmUrine

t+t

200 kmUrine

t+t

Ene

rgy

usag

e [M

J/p,

yr]

Fertiliser

Oil

Electricity

System boarders

• What to include and what to exclude?• UDD

– Solid organic waste– Energy production– Fertiliser production

• Food production– Delivered sanitational function

• Greywater• Drinking water• Other waste

Productive Sanitation

N=2.8kgP=0.4kgK=0.5 kg

N=2.8kgP=0.4kgK=0.5 kg

Nutrient flow per person and year

FoodExcreta

Fertiliser

Value of fertiliser - urine• 2.8kg N = 6kg Urea 0.5€/kg = 3€• 0.4 kg P = 2kg TPS ~0.4€/kg = 0.8€• 0.5 kg K = 1kg KCl ~0.4€/kg = 0.4€• Total value 4.2€ per person and

year = 0.012€ per person day• Value per jerry can 20L ~ 0.23€• Can at least pay for transport and

spreading• Non-subsidised

Cost for ecosan• Pour flush toilet 1900 INR (35€)• EcoSan toilet 4200 INR (77€)

Fertiliser per family

Nutrients Fertiliser Amount, kg Difference4 persons NPK 10-5-20 160 kg

N 18,2 10,0% 16,0 2,2P 2,32 2,2% 3,6 -1,2

NPK 10-5-20 Indian, price 5.5 INR/kg (0.1€)

Value 880 INR/year (16€)

Present value years 2-10: 5070 INR! (93€)

Conclusion

• Pour flush toilet cost: 1900 R• EcoSan toilet cost: 4200 R

– Income from fertiliser: 5080 R• Fertiliser can pay for toilet in 10 years, not just

additional cost!Additionally• Less hazard to ground & surface water

– Saves on drinking water– Protects health

Cost sharing• Having no toilet has lowest investment &

direct running costs!• Only type of toilet where the investment can

directly pay off• The cost of Ecosan is compatitive compared

with any other ecological solution• The cost is largely paid by household when

building – no risk for corruption at municipal level – higher cost acceptance

• More private enterprise – more competition – saves taxes