The principal–agent model with multilateral externalities: An application to climate agreements

We consider contracting of a principal with an agent if multilateral externalities are present. The motivating example is that of an international climate agreement given private information about the willingness-to-pay (WTP) for emissions abatement. Due to multilateral externalities the principal uses her own emissions besides subsidies to incentivize the agent and to assure his participation. Optimal contracts equalize marginal abatement costs and, thus, can be implemented by a system of competitive permit trading. Moreover, optimal contracts can include a boundary part (i.e., the endogenous, type dependent participation constraint is binding), which is not a copy of the outside option of no contract. Compared to this outside option, a contract can increase emissions of the principal for types with a low WTP, and reduce her payoff for high types. Subsidies can be constant or even decreasing in emission reductions, and turn negative so that the agent reduces emissions and pays the principal.     

Experimental evidence for internal predation in microzooplankton communities

The fate of microzooplankton production, whether it is channeled to mesozooplankton or recycled within the microbial food web, has major implications for the oceanic carbon cycle. The aim of this study was to estimate internal predation within naturally occurring microzooplankton communities. A dilution series based on the Landry and Hasset technique was created by mixing 200-μm-screened water (used as whole water) with 5-μm-screened seawater due to the dominance of pico- and small nanoplankton at our study site. This modification of the original technique allows for gradual reduction in microzooplankton abundance and thus internal predation while maintaining sufficient phytoplankton prey levels for microzooplankton growth in diluted treatments. Microzooplankton growth and mortality rates were calculated based on the changes in abundance during 24-h incubation. In the diluted treatments, microzooplankton growth rates were significantly higher (1.21 ± 0.20 day^?1 for ciliates and 0.88 ± 0.05 day^?1 for heterotrophic dinoflagellates) compared to those in whole seawater where microzooplankton abundance remained unchanged or even declined over time. Approximately 79 % of microzooplankton production was consumed within the microzooplankton, with aloricate ciliates being the most vulnerable to predation. These findings support the assumption that trophic interactions between microzooplankton can be an important factor controlling their production and, thus, energy transfer in picoplankton-dominated pelagic ecosystems.     

Oligopoly meets oligopsony: The case of permits

This paper derives market equilibria (in demand functions and in bidding strategies) between oligopolists and oligopsonists in a market with intermediates and no competition in final markets. To the best of my knowledge, this theme has not been explored, despite two observations: Firstly, the commonly applied framework of non-competitive and competitive fringe firms has implausible properties for the limit of purely strategic players. Secondly, real world cases correspond at least potentially to such strategic interactions, e.g., non-competitive players selling and buying permits (CO₂ and SO₂). The major implications are that these non-competitive markets are characterized by a kind of double marginalization (on the demand and the supply side) resulting in too little trade and wrong price signals.     

Organic pollutants in compost and digestate. Part 1. Polychlorinated biphenyls, polycyclic aromatic hydrocarbons and molecular markers

In Europe, 9.3 x 10(6) t(dry weight (dw)) of compost and digestate are produced per year. Most of this is applied to agricultural land, which can lead to considerable inputs of organic pollutants, such as polychlorinated biphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH) to soil. This paper presents an inventory of the pollutant situation in source-separated composts, digestates and presswater in Switzerland by a detailed analysis of over 70 samples. PCB concentrations ( summation PCB 28, 52, 101, 118, 138, 153, 180) were significantly higher in urban (median: 30 microg kg(-1)dw, n = 52) than in rural samples (median: 14 microg kg(-1)dw, n = 16). Together with low concentrations in general, this points to aerial deposition on compost input material as the major contamination pathway. Enantiomeric fractions of atropisometric PCB were close to racemic. Median PAH concentration was 3010 microg kg(-1)dw( summation 15PAH, n = 69), and one quarter of the samples exhibited concentrations above the relevant Swiss guide value for compost (4000 microg kg(-1)dw). The levels were influenced by the treatment process (digestate > compost), the season of input material collection (spring-summer > winter > autumn), the particle size (coarse-grained > fine-grained), and maturity (mature > less mature). The main source of PAH in compost was pyrogenic, probably influenced mainly by liquid fossil fuel combustion and some asphalt abrasion, as suggested by multiple linear regression. This study, together with a companion paper reporting on other organic contaminates including emerging compound classes, provides a starting point for a better risk-benefit estimation of the application of compost and digestate to agricultural soil in Switzerland.