Carbon sequestration in reclaimed soils

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Andrew Trlica, Sally Brown. U. of Washington, College of Forest Resources. - PowerPoint PPT Presentation

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  • Carbon sequestration in reclaimed soilsAndrew Trlica, Sally BrownU. of Washington, College of Forest ResourcesINTRODUCTION: World soils contain more than three times as much carbon as both the atmosphere and in Earths biomass (Lal, 2004). Management of soils and land-use practices to enhance soil organic carbon content could remove up to one million tonnes of carbon per year from the atmosphere, a significant move to slow the rise in atmospheric carbon dioxide levels (Pacala and Socolow, 2004). Similarly, reclamation of degraded soils worldwide could potentially capture 3 million tonnes of carbon per year during the 20-50 years of initial soil recovery (Lal, 1997). Using organic residuals in reclamation encourages greater carbon accrual on degraded lands (Tian et al. 2009), and the use of such residuals in surface mine reclamation could carry additional greenhouse gas avoidance benefits (Brown and Subler, 2007).The current study was initiated to compare carbon storage on mine soils reclaimed with biosolids to similar soils reclaimed conventionally. By quantifying carbon storage and accrual on degraded soils amended with biosolids, a protocol for generating carbon credits for adopting this approach to reclamation. It is hoped that carbon credits from reclaimed soils could help defray the cost of reclamation and lead to better long-term outcomes.METHODS: Soils were collected from several areas disturbed by surface mining and subsequently reclaimed with biosolids amendment. Site history and reclamation details were collected from knowledgeable sources. Samples were collected from random locations at each site, at depths of 0-15cm and 15-30cm. Bulk density samples were also taken. Total carbon (percent by weight) was measured using an automated dry combustion analyzer. In cases where warranted, soils were treated with HCl to remove carbonate carbon, and a thermal approach was used to quantify coal-C contamination where it was suspected. Site-wide C storage was calculated by the following equation: %C * Bulk density (Mg/m3) * .15m = C storage (Mg/ha)

    RESULTS: Sites reclaimed with biosolids amendment stored significantly more carbon, mostly in the top 15cm than conventionally reclaimed soils (See Table). Below 15cm there were typically no differences apparent. For every tonne of biosolids applied, between 0.10 and 0.33 tonnes of carbon were stored in soilCONCLUSIONS: Biosolids amendment enhanced carbon storage on reclaimed mine soils. The higher carbon storage is probably a combination of the additional carbon added with the amendment and the generally higher plant biomass inputs to the soil organic carbon pool that follow biosolids reclamation. The effect of biosolids is remarkably persistent, with sites up to ~30 years old still showing marked net carbon storage over conventional. Biosolids could be a useful tool for establishing carbon credit for mine reclamation, but the response of a soil to biosolids input is very sensitive to local conditions.REFERENCES: Brown, S. and Subler, S. 2007. In: Mine Closure 2007, pp. 459.Lal, R. 2004. Science 304:1623Lal, R. 1997. Soil Till. Res. 43:91Pacala S. and Socolow, R. 2004. Science 305:968Tian, G et al. 2009. JEQ 38:61

    HV

    Sitemean C storageSt. dev95% CI(+-)Net C storageSOC gain/yrGross C gain/appliedNet C gain/appliednt_crit

    Highland Valley

    HVC

    0-15cm4.601.561.640.000.77nana62.5705818347

    15-30cm10.262.252.360.001.71nana62.5705818347

    total14.862.742.490.002.48nana

    HVTA00

    0-15cm45.5314.7613.6540.935.690.34230.307772.4469118464

    15-30cm17.8119.7218.247.552.230.13390.056772.4469118464

    total63.3424.6320.2848.477.920.47620.3645142.1603686522

    HVTA04

    0-15cm40.4415.5814.4135.8410.110.29310.259772.4469118464

    15-30cm11.488.157.541.222.870.08320.008872.4469118464

    total51.9317.5814.4837.0612.980.37630.2686

    Summary of C stormean C storSt.dev95%CI(+-)net mean Cnet 95%CIGross Accum/yrnet SOC accum/yrgross accum/bs appl'dnet accum/bs appl'd

    0-15cm, treat42.9814.828.5538.3812.947.1646.400.320.28

    0-15cm, ctrl4.601.561.640.000.7670.00na

    15-30cm, all13.3312.525.860.002.2220.00na

    total, treat56.3219.409.5938.389.3866.400.420.28

    total, ctrl17.9312.6210.720.002.9890.00na

    ** comparisons of C storage use the treat/control means of the 0-15cm layer and grand mean of 15-30cm layer.

    Averages for sites

    AgeOM applied

    T6135.5

    C60

    MA

    Sitemean C storageSt. dev95% CI(+-)Net C storageSOC gain/yr*Gross C gain/appliedNet C gain/appliednt_crit

    RMI Topsoils

    Control

    0-15cm16.95615.151318136.12919124801.884nana212.706204734

    15-30cm4.592.4284921.819116967500.51nana212.706204734

    total21.54615.344705954146.685248502.394nana

    Treated

    0-15cm104.417543.54131340.268998126787.461529.15383333330.1757870370.147241582572.4469118464

    15-30cm20.130211.9748511.074889087915.54025.18006666670.03388922560.026161952972.4469118464

    total124.547745.157977925137.1882038103.001734.33390.20967626260.1734035354

    Summary of C stormean C storSt.dev95%CI(+-)net mean Cnet 95%CIGross accum/yrnet SOC accum/yrgross accum/bs appl'dnet accum/bs appl'd

    0-15cm, treat104.417543.54131340.268998126787.461577.194430934.805833333325.73147696670.1757870370.1472415825

    0-15cm, ctrl16.95615.151318136.129191248001.8840na

    15-30cm, all16.676812.459641.801043317003.84849526810na

    total, treat121.094345.288945303432.448013287.461577.194430940.364766666725.73147696670.20386245790.1472415825

    total, ctrl33.632819.616448864822.6121715003.73697777780na

    ** comparisons of C storage use the treat/control means of the 0-15cm layer and grand mean of 15-30cm layer.

    * assumes 0 carbon stored at year 0

    parametersaverage site ageOM applied

    T3594

    C90

    all4.33

    CE

    Sitemean C storageSt. devnt_crit95% CI(+-)Net C storage95%CI(+-)gross SOC gain/yr*Gross C gain/appliedNet C gain/applied

    Centralia

    Control

    0-15cm42.718.75162.134.67

    15-30cm31.668.55162.134.55

    total

    Surface app

    0-15cm54.0913.74122.208.73

    15-30cm25.646.08122.203.86

    total

    Deep injection

    0-15cm37.6910.25132.186.20

    15-30cm28.998.48132.185.12

    total

    Statistical summary

    Surface app

    0-15cm54.0913.7412.002.208.7313.637.603.180.100.02

    15-30cm29.058.0841.002.022.550.001.710.050.00

    total83.146.320.004.890.150.15

    0.00

    Aggr. Control

    0-15cm40.469.6229.002.053.660.001.491.00

    15-30cm29.058.0841.002.022.550.001.070.72

    total69.514.240.002.571.72

    **15-30cm aggregated for all treat and control

    **0-15cm aggregated for Control and deep-injection

    0.8019421176

    meanATAC

    age1727.07

    OM appl56040.34

    PA

    Sitemean C storageSt. devnt_crit95% CI(+-)Net C storage95%CI(+-)gross SOC gain/yr*net SOC gain/yrGross C gain/appliedNet C gain/applied

    Pennsylvania

    Control

    0-15cm*36.32712.1178892.30600413339.3146271223

    0-15cm**44.810314.8088892.306004133311.3831128298

    15-30cm**39.311419.1842492.306004133314.7463122447

    total**84.1217

    Surface app

    0-15cm*50.047117.07312192.10092203698.22898041713.7201

    0-15cm**68.057522.6643192.100922036910.923842910123.2472

    15-30cm**51.870931.99311192.100922036915.42018539480

    total**119.9284

    *corrected

    **uncorrected

    Statistical summary

    Surface app

    0-15cm68.057522.6643192.100922036910.923842910123.24723.68057433351.25721702450.33106083450.1130843395

    15-30cm47.833928.75935282.05183049311.15171162182.58687469580.2326845807

    total115.89146.26744902930.5637454153

    Aggr. Control

    0-15cm44.810314.8088892.306004133311.38311282982.6885642287na

    15-30cm47.833928.75935282.05183049311.15171162182.8699766005na

    total92.64425.5585408292na

    Site wideaver. AgeOM applied

    Treat18.491205.574

    Control16.6670

    SE

    Sitemean C storageSt. devnt_crit95% CI(+-)Net C storage95%CI(+-)gross SOC gain/yr*net SOC gain/yrGross C gain/appliedNet C gain/applied

    Sechelt

    Control

    0-15cm35.3118.4492.3114.17

    15-30cm11.305.6392.314.33

    total46.61

    Treated

    0-15cm42.6213.96162.137.44

    15-30cm29.4010.78152.145.97

    total

    Statistical summary

    Treated

    0-15cm*39.9915.75252.066.500.004.850.000.160.00

    15-30cm29.4010.78152.145.9718.106.973.502.150.110.07

    total69.388.270.28

    Control

    0-15cm*39.9915.75252.066.505.00

    15-30cm11.305.6392.314.331.41

    total51.296.41

    * aggregated across treat/ctrl

    Site wideaver. AgeOM applied

    Treat

    0-15cm8.38246.125

    15-30cm8.4255.72

    8.39250.768

    Control

    0-15cm849.8

    15-30cm849.8

    total

    0-15cm8.24175.448

    15-30cm8.25178.5

    poster summary

    0-15cm layer

    MineC storage (Mg/ha)C gain:input (Mg/Mg)

    Washington

    Biosolids54.09 (13.74)0.10

    Conventional42.71 (8.75)

    Pennsylvania

    Biosolids68.06 (22.66)0.33

    Conventional44.81 (14.81)

    Massachusetts

    Biosolids104.42 (43.54)0.18

    Conventional16.96 (15.15)

    BC Copper

    Biosolids42.98 (1.48)0.32

    Conventional4.60 (1.56)

    BC Sand

    Biosolids39.99 (15.75)0.16

    Unrecl'd topsoil32.02 (2.90)

    all

    MineAverage Net C (Mg/ha)Average site age (yrs)Net C accrual (MgC/ha/yr)Net C gain:input (Mg/Mg)

    Washington13.6170.800.02

    Pennsylvania23.218.51.260.11

    Massachusetts87.5325.70.15

    Copper Mine38.466.400.28

    BC Sand18.108.42.150.07