Keith R Lassey - Academia.edu (original) (raw)

Papers by Keith R Lassey

Research paper thumbnail of Towards reconciling national emission inventories for methane with the global budget

Environmental sciences, Jun 1, 2005

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Research paper thumbnail of The 14CH4 Measurement Record, Geologic Sources of Methane, and a new Reconciliation of the Global Methane Budget

AGUFM, Dec 1, 2007

ABSTRACT An enduring consensus of the global methane budget, as expressed in recent IPCC Assessme... more ABSTRACT An enduring consensus of the global methane budget, as expressed in recent IPCC Assessment Reports, is that about 20%\ of emissions have geologic origin (ie, are free of 14CH4). Based on atmospheric 14CH4 measurements and confounded by ill-quantified 14CH4 emissions from the nuclear- power industry, this "fossil fraction" estimate is quite uncertain, typically 18± 9%. A very recent re-determination of 30± 5%\ (± 2sigma) for the fossil fraction which does not require that the nuclear-power emission be specified may still be compatible with the earlier assessment despite an upward revision by 50%. Anthropogenic emissions via identified pathways of fossil-fuel exploitation are assessed in the Fourth IPCC Assessment Report at 90± 16 Tg~yr-1. Natural emissions extrapolated conservatively from new and widespread measurements of terrestrial seeps are 50± 10 Tg~yr-1, at least three times larger than previously accepted. The aggregate fossil emission of 140± 19 Tg~yr-1 is conservative yet still accounts for 24± 5%\ of the global source of 582± 87 Tg~yr-1, a value that is compatible with both 14CH4-based estimates of the fossil fraction. Nevertheless, while the fossil contribution to the methane source inventory remains incompletely determined the currently accepted estimate of ~20%\ for the fossil fraction may need to be revised upward, with substantial consequences for pre-industrial and contemporary source inventories.

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Research paper thumbnail of The usage of transfer coefficients to describe radionuclide transport from a cow's diet to its milk

PubMed, Aug 1, 1980

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Research paper thumbnail of On the importance of background sampling in applications of the SF6 tracer technique to determine ruminant methane emissions

Animal Feed Science and Technology, Mar 1, 2013

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Research paper thumbnail of Livestock methane emission: From the individual grazing animal through national inventories to the global methane cycle

Agricultural and Forest Meteorology, Feb 1, 2007

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Research paper thumbnail of Unidimensional solute transport incorporating equilibrium and rate-limited isotherms with first-order loss: 1. Model conceptualizations and analytic solutions

Water Resources Research, Mar 1, 1988

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Research paper thumbnail of Livestock methane emission and its perspective in the global methane cycle

Australian Journal of Experimental Agriculture, 2008

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Research paper thumbnail of A 21st-century shift from fossil-fuel to biogenic methane emissions indicated by 13CH4

Science, Mar 10, 2016

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Research paper thumbnail of Conceptually simple mathematical models of filtration (and exchange) processes

Ecological Modelling, 1983

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Research paper thumbnail of Balancing the global methane budget: constraints imposed by isotopes and anthropogenic emission inventories

Journal of Integrative Environmental Sciences, Aug 1, 2010

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Research paper thumbnail of The sulphur hexafluoride tracer technique for estimating enteric methane emissions from ruminants

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Research paper thumbnail of Methane emission from dairy cows and wether sheep fed subtropical grass‐dominant pastures in midsummer in New Zealand

New Zealand Journal of Agricultural Research, Oct 1, 2002

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Research paper thumbnail of Parity violating observables in low energy nucleon-nucleon scattering

Physical review, Feb 1, 1978

We have calculated the parity violating observables in p-p and n-p scattering using a number of s... more We have calculated the parity violating observables in p-p and n-p scattering using a number of strong nucleon-nucleon potentials for a large class of weak parity violating potentials.

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Research paper thumbnail of Some rumen digestion characteristics and methane emission in sheep

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Research paper thumbnail of Verifying agricultural emissions of methane

Springer eBooks, 2000

The most direct way to establish the level of surface emissions of greenhouse gases is to measure... more The most direct way to establish the level of surface emissions of greenhouse gases is to measure and interpret concentration gradients in the atmosphere. We have tested the efficacy of this approach for inferring average methane fluxes from regions of pastoral agriculture a few tens of km in extent In its simplest form, vertical concentration profiles are measured upwind and downwind of the target region, based on air samples collected from light aircraft. Using simple mass balance models, the profile contrasts can be related to the mean surface flux over the intervening region. The inferred flux can then be compared with ‘bottom-up’ estimates based on livestock density and per-animal emissions. However, such simple models may poorly simulate air flows over the New Zealand terrain, and as an alternative, we deploy a state-of-the-art mesoscale meteorological model, RAMS, coupled to an atmospheric dispersion model. RAMS is used prognostically to guide the timing and siting of measurement campaigns, and diagnostically to simulate regional wind fields which are validated against local meteorological data. Source-oriented and receptor-oriented dispersion modelling techniques, in combination with aircraft-based sampling and laboratory gas analysis, provide ‘top-down’ methane flux estimates that compare favourably with ‘bottom-up’ estimates. These techniques thus enhance confidence in national emission inventories based on bottom-up estimation. However, the challenge for similar verification of nitrous oxide emission is more imposing.

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Research paper thumbnail of Methane Emission By Grazing Livestock

In a series of field campaigns since 1995, a team of atmospheric and ruminantnutrition scientists... more In a series of field campaigns since 1995, a team of atmospheric and ruminantnutrition scientists have measured methane emissions directly from individual ruminant livestock freely grazing representative New Zealand pastures. The technique collects integrated ‘breath’ samples during grazing, using an implanted SF6 source as a conservative calibrated tracer, an approach pioneered by Johnson et al. [1994]. Most of these measurements have been on grazing sheep (942 animal-days to Aug 1999), others on grazing dairy cows (283), with some measurements also on sheep under controlled feeding conditions (305) [eg, Lassey et al., 1997; Ulyatt et al., 1999]. The aim is to characterise the variability of emission rates, including their dependence on pasture quality and physiological condition. The research goal is two-fold: (i) to provide a better scientific basis for assessing the national emissions inventory; and (ii) to investigate options for mitigating livestock emissions. Here, we discuss the research strategy and overview the principal research findings. We note in particular, that as a source of enterically fermented methane, sheep may not be merely ‘small cattle’.

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Research paper thumbnail of Enteric methane emission rates determined by the SF6 tracer technique: Temporal patterns and averaging periods

Animal Feed Science and Technology, Jun 1, 2011

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Research paper thumbnail of Methane emission from sheep grazing four pastures in late summer in New Zealand

New Zealand Journal of Agricultural Research, Dec 1, 2005

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Research paper thumbnail of On the performance of SF6 permeation tubes used in determining methane emission from grazing livestock

Chemosphere - Global Change Science, Oct 1, 2001

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Research paper thumbnail of Seasonal variation in methane emission from dairy cows and breeding ewes grazing ryegrass/white clover pasture in New Zealand

New Zealand Journal of Agricultural Research, Oct 1, 2002

... from dairy cows and breeding ewes, the dominant livestock types in New Zealand agriculture, f... more ... from dairy cows and breeding ewes, the dominant livestock types in New Zealand agriculture, fed on typical ryegrass/white clover dominant ... for calorimetric measurements from cows of similar intake, bodyweight or level of milk production (eg, Moe & Tyrell 1979; Wilkerson et al. ...

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Research paper thumbnail of Towards reconciling national emission inventories for methane with the global budget

Environmental sciences, Jun 1, 2005

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The 14CH4 Measurement Record, Geologic Sources of Methane, and a new Reconciliation of the Global Methane Budget

AGUFM, Dec 1, 2007

ABSTRACT An enduring consensus of the global methane budget, as expressed in recent IPCC Assessme... more ABSTRACT An enduring consensus of the global methane budget, as expressed in recent IPCC Assessment Reports, is that about 20%\ of emissions have geologic origin (ie, are free of 14CH4). Based on atmospheric 14CH4 measurements and confounded by ill-quantified 14CH4 emissions from the nuclear- power industry, this "fossil fraction" estimate is quite uncertain, typically 18± 9%. A very recent re-determination of 30± 5%\ (± 2sigma) for the fossil fraction which does not require that the nuclear-power emission be specified may still be compatible with the earlier assessment despite an upward revision by 50%. Anthropogenic emissions via identified pathways of fossil-fuel exploitation are assessed in the Fourth IPCC Assessment Report at 90± 16 Tg~yr-1. Natural emissions extrapolated conservatively from new and widespread measurements of terrestrial seeps are 50± 10 Tg~yr-1, at least three times larger than previously accepted. The aggregate fossil emission of 140± 19 Tg~yr-1 is conservative yet still accounts for 24± 5%\ of the global source of 582± 87 Tg~yr-1, a value that is compatible with both 14CH4-based estimates of the fossil fraction. Nevertheless, while the fossil contribution to the methane source inventory remains incompletely determined the currently accepted estimate of ~20%\ for the fossil fraction may need to be revised upward, with substantial consequences for pre-industrial and contemporary source inventories.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The usage of transfer coefficients to describe radionuclide transport from a cow's diet to its milk

PubMed, Aug 1, 1980

Bookmarks Related papers MentionsView impact

Research paper thumbnail of On the importance of background sampling in applications of the SF6 tracer technique to determine ruminant methane emissions

Animal Feed Science and Technology, Mar 1, 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Livestock methane emission: From the individual grazing animal through national inventories to the global methane cycle

Agricultural and Forest Meteorology, Feb 1, 2007

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Research paper thumbnail of Unidimensional solute transport incorporating equilibrium and rate-limited isotherms with first-order loss: 1. Model conceptualizations and analytic solutions

Water Resources Research, Mar 1, 1988

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Livestock methane emission and its perspective in the global methane cycle

Australian Journal of Experimental Agriculture, 2008

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A 21st-century shift from fossil-fuel to biogenic methane emissions indicated by 13CH4

Science, Mar 10, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Conceptually simple mathematical models of filtration (and exchange) processes

Ecological Modelling, 1983

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Balancing the global methane budget: constraints imposed by isotopes and anthropogenic emission inventories

Journal of Integrative Environmental Sciences, Aug 1, 2010

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The sulphur hexafluoride tracer technique for estimating enteric methane emissions from ruminants

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Methane emission from dairy cows and wether sheep fed subtropical grass‐dominant pastures in midsummer in New Zealand

New Zealand Journal of Agricultural Research, Oct 1, 2002

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Parity violating observables in low energy nucleon-nucleon scattering

Physical review, Feb 1, 1978

We have calculated the parity violating observables in p-p and n-p scattering using a number of s... more We have calculated the parity violating observables in p-p and n-p scattering using a number of strong nucleon-nucleon potentials for a large class of weak parity violating potentials.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Some rumen digestion characteristics and methane emission in sheep

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Verifying agricultural emissions of methane

Springer eBooks, 2000

The most direct way to establish the level of surface emissions of greenhouse gases is to measure... more The most direct way to establish the level of surface emissions of greenhouse gases is to measure and interpret concentration gradients in the atmosphere. We have tested the efficacy of this approach for inferring average methane fluxes from regions of pastoral agriculture a few tens of km in extent In its simplest form, vertical concentration profiles are measured upwind and downwind of the target region, based on air samples collected from light aircraft. Using simple mass balance models, the profile contrasts can be related to the mean surface flux over the intervening region. The inferred flux can then be compared with ‘bottom-up’ estimates based on livestock density and per-animal emissions. However, such simple models may poorly simulate air flows over the New Zealand terrain, and as an alternative, we deploy a state-of-the-art mesoscale meteorological model, RAMS, coupled to an atmospheric dispersion model. RAMS is used prognostically to guide the timing and siting of measurement campaigns, and diagnostically to simulate regional wind fields which are validated against local meteorological data. Source-oriented and receptor-oriented dispersion modelling techniques, in combination with aircraft-based sampling and laboratory gas analysis, provide ‘top-down’ methane flux estimates that compare favourably with ‘bottom-up’ estimates. These techniques thus enhance confidence in national emission inventories based on bottom-up estimation. However, the challenge for similar verification of nitrous oxide emission is more imposing.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Methane Emission By Grazing Livestock

In a series of field campaigns since 1995, a team of atmospheric and ruminantnutrition scientists... more In a series of field campaigns since 1995, a team of atmospheric and ruminantnutrition scientists have measured methane emissions directly from individual ruminant livestock freely grazing representative New Zealand pastures. The technique collects integrated ‘breath’ samples during grazing, using an implanted SF6 source as a conservative calibrated tracer, an approach pioneered by Johnson et al. [1994]. Most of these measurements have been on grazing sheep (942 animal-days to Aug 1999), others on grazing dairy cows (283), with some measurements also on sheep under controlled feeding conditions (305) [eg, Lassey et al., 1997; Ulyatt et al., 1999]. The aim is to characterise the variability of emission rates, including their dependence on pasture quality and physiological condition. The research goal is two-fold: (i) to provide a better scientific basis for assessing the national emissions inventory; and (ii) to investigate options for mitigating livestock emissions. Here, we discuss the research strategy and overview the principal research findings. We note in particular, that as a source of enterically fermented methane, sheep may not be merely ‘small cattle’.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Enteric methane emission rates determined by the SF6 tracer technique: Temporal patterns and averaging periods

Animal Feed Science and Technology, Jun 1, 2011

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Methane emission from sheep grazing four pastures in late summer in New Zealand

New Zealand Journal of Agricultural Research, Dec 1, 2005

Bookmarks Related papers MentionsView impact

Research paper thumbnail of On the performance of SF6 permeation tubes used in determining methane emission from grazing livestock

Chemosphere - Global Change Science, Oct 1, 2001

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Seasonal variation in methane emission from dairy cows and breeding ewes grazing ryegrass/white clover pasture in New Zealand

New Zealand Journal of Agricultural Research, Oct 1, 2002

... from dairy cows and breeding ewes, the dominant livestock types in New Zealand agriculture, f... more ... from dairy cows and breeding ewes, the dominant livestock types in New Zealand agriculture, fed on typical ryegrass/white clover dominant ... for calorimetric measurements from cows of similar intake, bodyweight or level of milk production (eg, Moe & Tyrell 1979; Wilkerson et al. ...

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